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 
yeah.  just realized that.  Do we want to merge this directly into master or into the branch?  The advantage of pushing into the branch is that this feature will get full end-to-end manual testing attention (as part of the end-of-epic story).