Bring CE-EE parity to app/services/boards/issues/create_service.rb

app/services/boards/issues/create_service.rb

 module Boards
   module Issues
     class CreateService < Boards::BaseService
+      prepend ::EE::Boards::Issues::CreateService
+
       attr_accessor :project
 
       def initialize(parent, project, user, params = {})
@@ -10,23 +12,13 @@ module Boards
       end
 
       def execute
-        create_issue(creation_params)
+        create_issue(params.merge(issue_params))
       end
 
       private
 
-      def creation_params
-        params.merge(label_ids: [list.label_id, *board.label_ids],
-                     weight: board.weight,
-                     milestone_id: board.milestone_id,
-                     assignee_ids: assignee_ids)
-      end
-
-      # This can be safely removed when the board
-      # receive multiple assignee support.
-      # See: https://gitlab.com/gitlab-org/gitlab-ee/issues/3786
-      def assignee_ids
-        @assigne_ids ||= Array(board.assignee&.id)
+      def issue_params
+        { label_ids: [list.label_id] }
       end
 
       def board

ee/app/services/ee/boards/issues/create_service.rb

+module EE
+  module Boards
+    module Issues
+      module CreateService
+        extend ::Gitlab::Utils::Override
+
+        override :issue_params
+        def issue_params
+          {
+            label_ids: [list.label_id, *board.label_ids],
+            weight: board.weight,
+            milestone_id: board.milestone_id,
+            # This can be removed when boards have multiple assignee support.
+            # See https://gitlab.com/gitlab-org/gitlab-ee/issues/3786
+            assignee_ids: Array(board.assignee&.id)
+          }
+        end
+      end
+    end
+  end
+end