Original suggestion from akostadi1@redhat.com:
One issue I see with emptying is that the implementation only seems to handle MessageRecipient objects. I see nothing to delete sent messages. Perhaps that can be implemented by adding an additional `state` to Message, probably `deleted` would be self-explanatory.

Deleting of orphaned messages is implemented in app/workers/janitor_worker.rb based on the `Message#stale` scope. It probably would need to be adjusted to also catch that new`Messages#deleted` state.