Merge branch 'ce-10283-notifications-for-ci-minutes-quota-limit-approaching' into 'master'

Backport of https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/14328

See merge request gitlab-org/gitlab-ce!30003

db/migrate/20190621022810_add_last_ci_minutes_usage_notification_level_to_namespaces.rb

+# frozen_string_literal: true
+
+class AddLastCiMinutesUsageNotificationLevelToNamespaces < ActiveRecord::Migration[5.1]
+  DOWNTIME = false
+
+  def change
+    add_column :namespaces, :last_ci_minutes_usage_notification_level, :integer
+  end
+end

db/schema.rb

@@ -2116,6 +2116,7 @@ ActiveRecord::Schema.define(version: 20190703130053) do
     t.integer "extra_shared_runners_minutes_limit"
     t.string "ldap_sync_status", default: "ready", null: false
     t.boolean "membership_lock", default: false
+    t.integer "last_ci_minutes_usage_notification_level"
     t.index ["created_at"], name: "index_namespaces_on_created_at", using: :btree
     t.index ["custom_project_templates_group_id", "type"], name: "index_namespaces_on_custom_project_templates_group_id_and_type", where: "(custom_project_templates_group_id IS NOT NULL)", using: :btree
     t.index ["file_template_project_id"], name: "index_namespaces_on_file_template_project_id", using: :btree