closedby_id added to safe attributes

lib/gitlab/import_export/relation_factory.rb

@@ -18,7 +18,7 @@ module Gitlab
                     label: :project_label,
                     custom_attributes: 'ProjectCustomAttribute' }.freeze
 
-      USER_REFERENCES = %w[author_id assignee_id updated_by_id user_id created_by_id last_edited_by_id merge_user_id resolved_by_id].freeze
+      USER_REFERENCES = %w[author_id assignee_id updated_by_id user_id created_by_id last_edited_by_id merge_user_id resolved_by_id closed_by_id].freeze
 
       PROJECT_REFERENCES = %w[project_id source_project_id target_project_id].freeze
 

spec/lib/gitlab/import_export/safe_model_attributes.yml

@@ -15,7 +15,7 @@ Issue:
 - updated_by_id
 - confidential
 - closed_at
-- closed_by
+- closed_by_id
 - due_date
 - moved_to_id
 - lock_version