Add a notification central

The current situation

There are many different types of notifications a user can receive while on Gitlab. Unfortunately, the majority are only received per email. Since email is asynchronous, my common flow is to read the email when I have time, log into Gitlab at a later time and... can't find a copy of what I received in my email, nor a way to manage them.

Currently all that is visible are image

  • Assigned issues
  • Merge requests and merge reviews
  • "TODO"

Problems

  • The TODO list seems to duplicate the two top items but not completely? At least to me its use isn't very clear
  • Only a subset of actions are visible. Responses to comments, "@user", comments on commits, new merge requests, etc. all can't be found easily

Proposal

Add one central, easily visible and accessible area where one can see and manage notifications:

  • Display all notifications
  • Group notifications by type (tab per group)
  • Filter which notifications to show/ignore
  • Configure how long notifications are to be shown
  • Mark notifications as read