Enable some frozen string in ee/app

Enables frozen string in the following:

* ee/app/helpers/**/*.rb
* ee/app/mailers/**/*.rb
* ee/app/models/**/*.rb

Partially addresses gitlab-org/gitlab-ce/#47424.

ee/app/helpers/audit_events_helper.rb

+# frozen_string_literal: true
+
 module AuditEventsHelper
   def human_text(details)
     details.map { |key, value| select_keys(key, value) }.join(" ").humanize

ee/app/helpers/audit_logs_helper.rb

+# frozen_string_literal: true
+
 module AuditLogsHelper
   def event_type_options
     [

ee/app/helpers/auditor_user_helper.rb

+# frozen_string_literal: true
+
 module AuditorUserHelper
   include ::Gitlab::Utils::StrongMemoize
 

ee/app/helpers/batch_comments_helper.rb

+# frozen_string_literal: true
+
 module BatchCommentsHelper
   def batch_comments_enabled?
     current_user.present? && @project.feature_available?(:batch_comments, current_user)

ee/app/helpers/billing_plans_helper.rb

+# frozen_string_literal: true
+
 module BillingPlansHelper
   def subscription_plan_info(plans_data, current_plan_code)
     plans_data.find { |plan| plan.code == current_plan_code }

ee/app/helpers/ee/appearances_helper.rb

+# frozen_string_literal: true
+
 module EE
   module AppearancesHelper
     def header_message
@@ -26,10 +28,10 @@ module EE
     end
 
     def message_style
-      style = ''
+      style = []
       style << "background-color: #{current_appearance.message_background_color};"
       style << "color: #{current_appearance.message_font_color}"
-      style
+      style.join
     end
   end
 end

ee/app/helpers/ee/application_helper.rb

+# frozen_string_literal: true
+
 module EE
   module ApplicationHelper
     extend ::Gitlab::Utils::Override

ee/app/helpers/ee/application_settings_helper.rb

+# frozen_string_literal: true
+
 module EE
   module ApplicationSettingsHelper
     extend ::Gitlab::Utils::Override

ee/app/helpers/ee/auth_helper.rb

+# frozen_string_literal: true
+
 module EE
   module AuthHelper
     extend ::Gitlab::Utils::Override

ee/app/helpers/ee/award_emoji_helper.rb

+# frozen_string_literal: true
+
 module EE
   module AwardEmojiHelper
     extend ::Gitlab::Utils::Override

ee/app/helpers/ee/boards_helper.rb

+# frozen_string_literal: true
+
 module EE
   module BoardsHelper
     extend ::Gitlab::Utils::Override

ee/app/helpers/ee/branches_helper.rb

+# frozen_string_literal: true
+
 module EE
   module BranchesHelper
     # Returns a hash were keys are types of access levels (user, role), and

ee/app/helpers/ee/button_helper.rb

+# frozen_string_literal: true
+
 module EE
   module ButtonHelper
     extend ::Gitlab::Utils::Override

ee/app/helpers/ee/dashboard_helper.rb

+# frozen_string_literal: true
+
 module EE
   module DashboardHelper
     def controller_action_to_child_dashboards(controller = controller_name, action = action_name)

ee/app/helpers/ee/emails_helper.rb

+# frozen_string_literal: true
+
 module EE
   module EmailsHelper
     extend ::Gitlab::Utils::Override

ee/app/helpers/ee/environments_helper.rb

+# frozen_string_literal: true
+
 module EE
   module EnvironmentsHelper
     def metrics_data(project, environment)

ee/app/helpers/ee/form_helper.rb

+# frozen_string_literal: true
+
 module EE
   module FormHelper
     def issue_assignees_dropdown_options

ee/app/helpers/ee/gitlab_routing_helper.rb

+# frozen_string_literal: true
+
 module EE
   module GitlabRoutingHelper
     include ::ProjectsHelper

ee/app/helpers/ee/groups_helper.rb

+# frozen_string_literal: true
+
 module EE
   module GroupsHelper
     extend ::Gitlab::Utils::Override

ee/app/helpers/ee/import_helper.rb

+# frozen_string_literal: true
+
 module EE
   module ImportHelper
     extend ::Gitlab::Utils::Override

ee/app/helpers/ee/issuables_helper.rb

+# frozen_string_literal: true
+
 module EE
   module IssuablesHelper
     extend ::Gitlab::Utils::Override

ee/app/helpers/ee/issues_helper.rb

+# frozen_string_literal: true
+
 module EE
   module IssuesHelper
     def weight_dropdown_tag(issuable, opts = {}, &block)

ee/app/helpers/ee/lock_helper.rb

+# frozen_string_literal: true
+
 module EE
   module LockHelper
     def lock_file_link(project = @project, path = @path, html_options: {})

ee/app/helpers/ee/merge_requests_helper.rb

+# frozen_string_literal: true
+
 module EE
   module MergeRequestsHelper
     def render_items_list(items, separator = "and")

ee/app/helpers/ee/milestones_helper.rb

+# frozen_string_literal: true
+
 module EE
   module MilestonesHelper
     def burndown_chart(milestone)
@@ -32,9 +34,9 @@ module EE
         end
 
       if message
-        message += link_to "About burndown charts", help_page_path('user/project/milestones/index', anchor: 'burndown-charts'), class: 'burndown-docs-link'
+        link = link_to "About burndown charts", help_page_path('user/project/milestones/index', anchor: 'burndown-charts'), class: 'burndown-docs-link'
 
-        content_tag(:div, message.html_safe, id: "data-warning", class: "settings-message prepend-top-20")
+        content_tag(:div, (message + link).html_safe, id: "data-warning", class: "settings-message prepend-top-20")
       end
     end
 

ee/app/helpers/ee/namespaces_helper.rb

+# frozen_string_literal: true
+
 module EE
   module NamespacesHelper
     def namespace_shared_runner_limits_quota(namespace)

ee/app/helpers/ee/nav_helper.rb

+# frozen_string_literal: true
+
 module EE
   module NavHelper
     extend ::Gitlab::Utils::Override

ee/app/helpers/ee/notes_helper.rb

+# frozen_string_literal: true
+
 module EE
   module NotesHelper
     extend ::Gitlab::Utils::Override

ee/app/helpers/ee/projects_helper.rb

+# frozen_string_literal: true
+
 module EE
   module ProjectsHelper
     extend ::Gitlab::Utils::Override

ee/app/helpers/ee/saml_providers_helper.rb

+# frozen_string_literal: true
+
 module EE
   module SamlProvidersHelper
     def group_saml_configured?

ee/app/helpers/ee/services_helper.rb

+# frozen_string_literal: true
+
 module EE
   module ServicesHelper
     def add_to_slack_link(project, slack_app_id)

ee/app/helpers/ee/system_note_helper.rb

+# frozen_string_literal: true
+
 module EE
   module SystemNoteHelper
     extend ::Gitlab::Utils::Override

ee/app/helpers/ee/todos_helper.rb

+# frozen_string_literal: true
+
 module EE
   module TodosHelper
     extend ::Gitlab::Utils::Override

ee/app/helpers/ee/user_callouts_helper.rb

+# frozen_string_literal: true
+
 module EE
   module UserCalloutsHelper
     GOLD_TRIAL = 'gold_trial'.freeze

ee/app/helpers/epics_helper.rb

+# frozen_string_literal: true
+
 module EpicsHelper
   def epic_show_app_data(epic, opts)
     group = epic.group

ee/app/helpers/group_members_helper.rb

+# frozen_string_literal: true
+
 module GroupMembersHelper
   def clear_ldap_permission_cache_message
     markdown(

ee/app/helpers/license_helper.rb

+# frozen_string_literal: true
+
 module LicenseHelper
   include ActionView::Helpers::AssetTagHelper
   include ActionView::Helpers::UrlHelper

ee/app/helpers/mirror_helper.rb

+# frozen_string_literal: true
+
 module MirrorHelper
   def render_mirror_failed_message(raw_message:)
     mirror_last_update_at = @project.import_state.last_update_at
@@ -15,14 +17,14 @@ module MirrorHelper
   end
 
   def branch_diverged_tooltip_message
-    message = s_('Branches|The branch could not be updated automatically because it has diverged from its upstream counterpart.')
+    message = [s_('Branches|The branch could not be updated automatically because it has diverged from its upstream counterpart.')]
 
     if can?(current_user, :push_code, @project)
       message << '<br>'
       message << s_("Branches|To discard the local changes and overwrite the branch with the upstream version, delete it here and choose 'Update Now' above.")
     end
 
-    message
+    message.join
   end
 
   def options_for_mirror_user

ee/app/helpers/path_locks_helper.rb

+# frozen_string_literal: true
+
 module PathLocksHelper
   def can_unlock?(path_lock, current_user = @current_user, project = @project)
     can?(current_user, :admin_path_locks, project) || path_lock.user == current_user

ee/app/helpers/protected_environments_helper.rb

+# frozen_string_literal: true
+
 module ProtectedEnvironmentsHelper
   def protected_environments_enabled?(project)
     project.protected_environments_feature_available?

ee/app/helpers/push_rules_helper.rb

+# frozen_string_literal: true
+
 module PushRulesHelper
   def reject_unsigned_commits_description(push_rule)
     message = s_("ProjectSettings|Only signed commits can be pushed to this repository.")

ee/app/mailers/ee/notify.rb

+# frozen_string_literal: true
+
 module EE
   module Notify
     extend ActiveSupport::Concern

ee/app/mailers/ee/preview/notify_preview.rb

+# frozen_string_literal: true
+
 module EE
   module Preview
     module NotifyPreview

ee/app/mailers/emails/admin_notification.rb

+# frozen_string_literal: true
+
 module Emails
   module AdminNotification
     def send_admin_notification(user_id, subject, body)

ee/app/mailers/emails/csv_export.rb

+# frozen_string_literal: true
+
 module Emails
   module CsvExport
     def issues_csv_email(user, project, csv_data, export_status)

ee/app/mailers/emails/ee/notes.rb

+# frozen_string_literal: true
+
 module Emails
   module EE
     module Notes

ee/app/mailers/emails/ee/projects.rb

+# frozen_string_literal: true
+
 module Emails
   module EE
     module Projects

ee/app/mailers/emails/service_desk.rb

+# frozen_string_literal: true
+
 module Emails
   module ServiceDesk
     extend ActiveSupport::Concern

ee/app/models/approval.rb

+# frozen_string_literal: true
+
 class Approval < ActiveRecord::Base
   belongs_to :user
   belongs_to :merge_request

ee/app/models/approver.rb

+# frozen_string_literal: true
+
 class Approver < ActiveRecord::Base
   belongs_to :target, polymorphic: true  # rubocop:disable Cop/PolymorphicAssociations
   belongs_to :user

ee/app/models/approver_group.rb

+# frozen_string_literal: true
+
 class ApproverGroup < ActiveRecord::Base
   belongs_to :target, polymorphic: true  # rubocop:disable Cop/PolymorphicAssociations
   belongs_to :group

ee/app/models/board_assignee.rb

+# frozen_string_literal: true
+
 class BoardAssignee < ActiveRecord::Base
   belongs_to :board
   belongs_to :assignee, class_name: 'User'

ee/app/models/board_label.rb

+# frozen_string_literal: true
+
 class BoardLabel < ActiveRecord::Base
   belongs_to :board
   belongs_to :label

ee/app/models/burndown.rb

+# frozen_string_literal: true
+
 class Burndown
   include Gitlab::Utils::StrongMemoize
 

ee/app/models/ci/pipeline_chat_data.rb

+# frozen_string_literal: true
+
 module Ci
   class PipelineChatData < ActiveRecord::Base
     self.table_name = 'ci_pipeline_chat_data'

ee/app/models/ci/sources/pipeline.rb

+# frozen_string_literal: true
+
 module Ci
   module Sources
     class Pipeline < ActiveRecord::Base

ee/app/models/concerns/approvable.rb

+# frozen_string_literal: true
+
 module Approvable
   # A method related to approvers that is user facing
   # should be moved to VisibleApprovable because

ee/app/models/concerns/custom_model_naming.rb

+# frozen_string_literal: true
+
 module CustomModelNaming
   # Extracted from: https://github.com/stevenbarragan/spree_random_subscriptions/blob/5426ccaf8a2084c495b2cac9dfbd27e30ade0cec/lib/custom_model_naming.rb
 

ee/app/models/concerns/ee/deployment_platform.rb

+# frozen_string_literal: true
+
 module EE
   module DeploymentPlatform
     extend ::Gitlab::Utils::Override

ee/app/models/concerns/ee/kubernetes_service.rb

+# frozen_string_literal: true
+
 module EE
   module KubernetesService
     extend ActiveSupport::Concern

ee/app/models/concerns/ee/participable.rb

+# frozen_string_literal: true
+
 module EE
   module Participable
     extend ::Gitlab::Utils::Override

ee/app/models/concerns/ee/prometheus_adapter.rb

+# frozen_string_literal: true
+
 module EE
   module PrometheusAdapter
     extend ::Gitlab::Utils::Override

ee/app/models/concerns/ee/protected_branch.rb

+# frozen_string_literal: true
+
 module EE
   module ProtectedBranch
     extend ActiveSupport::Concern

ee/app/models/concerns/ee/protected_ref.rb

+# frozen_string_literal: true
+
 module EE
   module ProtectedRef
     def protected_ref_access_levels(*types)

ee/app/models/concerns/ee/protected_ref_access.rb

+# frozen_string_literal: true
+
 # EE-specific code related to protected branch/tag access levels.
 #
 # Note: Don't directly include this concern into a model class.

ee/app/models/concerns/ee/relative_positioning.rb

+# frozen_string_literal: true
+
 module EE
   # Issue position on list boards should be relative to all group projects
   module RelativePositioning

ee/app/models/concerns/elastic/issues_search.rb

+# frozen_string_literal: true
+
 module Elastic
   module IssuesSearch
     extend ActiveSupport::Concern

ee/app/models/concerns/elastic/merge_requests_search.rb

+# frozen_string_literal: true
+
 module Elastic
   module MergeRequestsSearch
     extend ActiveSupport::Concern

ee/app/models/concerns/elastic/milestones_search.rb

+# frozen_string_literal: true
+
 module Elastic
   module MilestonesSearch
     extend ActiveSupport::Concern

ee/app/models/concerns/elastic/notes_search.rb

+# frozen_string_literal: true
+
 module Elastic
   module NotesSearch
     extend ActiveSupport::Concern

ee/app/models/concerns/elastic/projects_search.rb

+# frozen_string_literal: true
+
 module Elastic
   module ProjectsSearch
     extend ActiveSupport::Concern

ee/app/models/concerns/elastic/repositories_search.rb

+# frozen_string_literal: true
+
 module Elastic
   module RepositoriesSearch
     extend ActiveSupport::Concern

ee/app/models/concerns/elastic/snippets_search.rb

+# frozen_string_literal: true
+
 module Elastic
   module SnippetsSearch
     extend ActiveSupport::Concern

ee/app/models/concerns/elastic/wiki_repositories_search.rb

+# frozen_string_literal: true
+
 module Elastic
   module WikiRepositoriesSearch
     extend ActiveSupport::Concern

ee/app/models/concerns/geo/model.rb

+# frozen_string_literal: true
+
 module Geo
   module Model
     extend ActiveSupport::Concern

ee/app/models/concerns/geo/syncable.rb

+# frozen_string_literal: true
+
 module Geo::Syncable
   extend ActiveSupport::Concern
 

ee/app/models/concerns/has_environment_scope.rb

+# frozen_string_literal: true
+
 module HasEnvironmentScope
   extend ActiveSupport::Concern
 

ee/app/models/concerns/object_storable.rb

+# frozen_string_literal: true
+
 module ObjectStorable
   extend ActiveSupport::Concern
 

ee/app/models/concerns/visible_approvable.rb

+# frozen_string_literal: true
+
 # This module may only be used by presenters or modules
 # that include the Approvable concern
 module VisibleApprovable

ee/app/models/ee/appearance.rb

+# frozen_string_literal: true
+
 module EE
   module Appearance
     extend ActiveSupport::Concern

ee/app/models/ee/application_setting.rb

+# frozen_string_literal: true
+
 module EE
   # ApplicationSetting EE mixin
   #

ee/app/models/ee/audit_event.rb

+# frozen_string_literal: true
+
 module EE
   module AuditEvent
     extend ActiveSupport::Concern

ee/app/models/ee/board.rb

+# frozen_string_literal: true
+
 module EE
   module Board
     extend ActiveSupport::Concern

ee/app/models/ee/broadcast_message.rb

+# frozen_string_literal: true
+
 module EE
   # BroadcastMessage EE mixin
   #

ee/app/models/ee/ci/build.rb

+# frozen_string_literal: true
+
 module EE
   module Ci
     # Build EE mixin

ee/app/models/ee/ci/job_artifact.rb

+# frozen_string_literal: true
+
 module EE
   # CI::JobArtifact EE mixin
   #

ee/app/models/ee/ci/pipeline.rb

+# frozen_string_literal: true
+
 module EE
   module Ci
     module Pipeline

ee/app/models/ee/ci/runner.rb

+# frozen_string_literal: true
+
 module EE
   module Ci
     module Runner

ee/app/models/ee/clusters/applications/prometheus.rb

+# frozen_string_literal: true
+
 module EE
   module Clusters
     module Applications

ee/app/models/ee/clusters/cluster.rb

+# frozen_string_literal: true
+
 module EE
   module Clusters
     module Cluster

ee/app/models/ee/environment.rb

+# frozen_string_literal: true
+
 module EE
   module Environment
     extend ActiveSupport::Concern

ee/app/models/ee/epic.rb

+# frozen_string_literal: true
+
 module EE
   module Epic
     extend ActiveSupport::Concern

ee/app/models/ee/global_milestone.rb

+# frozen_string_literal: true
+
 module EE
   module GlobalMilestone
     def supports_weight?

ee/app/models/ee/group.rb

+# frozen_string_literal: true
+
 module EE
   # Group EE mixin
   #

ee/app/models/ee/group_milestone.rb

+# frozen_string_literal: true
+
 module EE
   module GroupMilestone
     def supports_weight?

ee/app/models/ee/identity.rb

+# frozen_string_literal: true
+
 module EE
   module Identity
     extend ActiveSupport::Concern

ee/app/models/ee/issue.rb

+# frozen_string_literal: true
+
 module EE
   module Issue
     extend ActiveSupport::Concern

ee/app/models/ee/lfs_object.rb

+# frozen_string_literal: true
+
 module EE
   # LFS Object EE mixin
   #

ee/app/models/ee/list.rb

+# frozen_string_literal: true
+
 module EE
   module List
     extend ::Gitlab::Utils::Override

ee/app/models/ee/merge_request.rb

+# frozen_string_literal: true
+
 module EE
   module MergeRequest
     extend ActiveSupport::Concern