Add "new user" to notification settings

Problem to solve

It's helpful for administrators to know when new users join a GitLab instance, both to help with onboarding and with seat/license management. Some customers have requested that we add an additional event to our existing notification system to flag when this event occurs.

Proposal

• Add new_user as a notifiable event.

The notification should capture the user's name, user_id, registration method (registration form, ldap, etc), and when the user was created.

Links / references