Added comment about inactive model/service

app/models/concerns/label_eventable.rb

@@ -4,6 +4,8 @@
 #
 # Contains functionality related to objects that support adding/removing labels.
 #
+# This concern is not used yet, it will be used for:
+# https://gitlab.com/gitlab-org/gitlab-ce/issues/48483
 
 module LabelEventable
   extend ActiveSupport::Concern

app/models/resource_label_event.rb

 # frozen_string_literal: true
 
+# This model is not used yet, it will be used for:
+# https://gitlab.com/gitlab-org/gitlab-ce/issues/48483
 class ResourceLabelEvent < ActiveRecord::Base
   prepend EE::ResourceLabelEvent
 

app/services/resource_events/change_labels_service.rb

 # frozen_string_literal: true
 
+# This service is not used yet, it will be used for:
+# https://gitlab.com/gitlab-org/gitlab-ce/issues/48483
 module ResourceEvents
   class ChangeLabelsService
     prepend EE::ResourceEvents::ChangeLabelsService