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app/views/files/index.json.jbuilder

@@ -14,6 +14,7 @@ json.data do
         json.partial! "users/user_simple", user: attachment.author
       end
       # json.partial! "files/course_groups", attachment_group_settings: attachment.attachment_group_settings
+      json.category_id attachment.course_second_category_id
       if @course_second_category_id.to_i == 0
         json.category_name attachment.course_second_category&.name
       end