We currently are accumulating orphaned upload references whenever drafts are deleted.
This change deals with future cases by adding a dependent strategy of delete_all on the Draft#upload_references association. (We don't really need destroy strategy here, since UploadReference is a simple data bag and there are no validations or callbacks on the model.)
It deals with existing cases through a migration that deletes all existing, orphaned draft upload references.
Ted Johansson