Two models are connected in a one-to-many relationship, if you delete this very one – it is clear that all many will be deleted if you do not specify
WillCascadeOnDelete(false) . But I need an inverse problem to automatically delete one when all many dependent on it are deleted.
It comes to mind to hang up some kind of trigger on the database, which will check when many are deleted, nothing refers to a single element => crashes next.
You can make a JOB that will check items from time to time and remove " garbage ".