Add a new user API for the notifier

This new endpoint is designed specifically to fill the needs of the
notifier and should not be used by other clients.

@jimabramson @nasthagiri 
I'm not sure that's better:

` @ddt.data(*itertools.product([True, False], [True, False], [True, False]))`

It's not immediately clear what all of those booleans mean, though it does become clear when reading the function signature.