This lets unread notifications sync to the database, so you can see how many notifications you've missed on pageload.
alex.last_read_notification = nil)
Everything works, but I need to double-check a few things before merging.
EDIT: I ended up removing the foreign key constraint in a separate commit. If you merge this you should remove that part. It's not needed, and it causes the counter to reset if your most recent notification gets deleted.