Allow users to pick non-email notifications
At the moment, GitLab only has email notifications. We also have todos, which are kind-of notifications, but also not. (I love todos, and want to keep them.)
We could add user-level notification services, like the existing project services, to allow users to have notifications sent in other ways. Considerations:
- They would need to able to be controlled at the admin level, so a user can't enable the (for example) WhatsApp service if it's forbidden globally.
- We would need notification settings per-user per-project per-notification-service. If you only get these other notifications in exactly the same format as emails, you may as well just set up push notifications for your emails!
- We would probably want to integrate our existing services with these new services. https://gitlab.com/gitlab-org/gitlab-ce/issues/26321 and https://gitlab.com/gitlab-org/gitlab-ce/issues/13815 talk about this a bit more. That would let users subscribe to or unsubscribe from the existing project-level notification services.