Move helper methods related to issue types into a helper module

We will reuse this module in issue form later.

It also renames the method name to `create_issue_type_allowed?` to
clarify its intent.

app/services/concerns/issues/issue_type_helpers.rb

+# frozen_string_literal: true
+
+module Issues
+  module IssueTypeHelpers
+    # @param object [Issue, Project]
+    # @param issue_type [String, Symbol]
+    def create_issue_type_allowed?(object, issue_type)
+      WorkItem::Type.base_types.key?(issue_type.to_s) &&
+        can?(current_user, :"create_#{issue_type}", object)
+    end
+  end
+end

app/services/issues/base_service.rb

@@ -3,6 +3,7 @@
 module Issues
   class BaseService < ::IssuableBaseService
     include IncidentManagement::UsageData
+    include IssueTypeHelpers
 
     def hook_data(issue, action, old_associations: {})
       hook_data = issue.to_hook_data(current_user, old_associations: old_associations)
@@ -44,7 +45,7 @@ module Issues
     def filter_params(issue)
       super
 
-      params.delete(:issue_type) unless issue_type_allowed?(issue)
+      params.delete(:issue_type) unless create_issue_type_allowed?(issue, params[:issue_type])
       filter_incident_label(issue) if params[:issue_type]
 
       moved_issue = params.delete(:moved_issue)
@@ -89,12 +90,6 @@ module Issues
       Milestones::IssuesCountService.new(milestone).delete_cache
     end
 
-    # @param object [Issue, Project]
-    def issue_type_allowed?(object)
-      WorkItem::Type.base_types.key?(params[:issue_type]) &&
-        can?(current_user, :"create_#{params[:issue_type]}", object)
-    end
-
     # @param issue [Issue]
     def filter_incident_label(issue)
       return unless add_incident_label?(issue) || remove_incident_label?(issue)

app/services/issues/build_service.rb

@@ -80,7 +80,7 @@ module Issues
       ]
 
       allowed_params << :milestone_id if can?(current_user, :admin_issue, project)
-      allowed_params << :issue_type if issue_type_allowed?(project)
+      allowed_params << :issue_type if create_issue_type_allowed?(project, params[:issue_type])
 
       params.slice(*allowed_params)
     end