Fixes activation of project mirror when project is created.

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With feature enabled

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #3233 (closed)

app/services/projects/create_service.rb

 module Projects
   class CreateService < BaseService
+    prepend ::EE::Projects::CreateService
+
     def initialize(user, params)
       @current_user, @params = user, params.dup
     end
@@ -11,19 +13,10 @@ def execute
 
       forked_from_project_id = params.delete(:forked_from_project_id)
       import_data = params.delete(:import_data)
-      mirror = params.delete(:mirror)
-      mirror_user_id = params.delete(:mirror_user_id)
-      mirror_trigger_builds = params.delete(:mirror_trigger_builds)
       @skip_wiki = params.delete(:skip_wiki)
 
       @project = Project.new(params)
 
-      if mirror && @project.feature_available?(:repository_mirrors)
-        @project.mirror = mirror
-        @project.mirror_user_id = mirror_user_id
-        @project.mirror_trigger_builds = mirror_trigger_builds
-      end
-
       # Make sure that the user is allowed to use the specified visibility level
       unless Gitlab::VisibilityLevel.allowed_for?(current_user, @project.visibility_level)
         deny_visibility_level(@project)
@@ -56,6 +49,8 @@ def execute
         @project.namespace_id = current_user.namespace_id
       end
 
+      yield(@project)
+
       @project.creator = current_user
 
       if forked_from_project_id