feat(webapp): allows mark all notifications as read

Created by: ftonato

Pullrequest

This pull-request will allows all the users mark all notifications as read with one click

Preview:

Issues

• fixes #2660 (closed)

Todo

• backend:
  • mutation: have a singe mutation with both functionallities in markAsRead?
    • instead of extra mutation markAllAsRead
    • especially because for paginated notification list we may just want to mark a given array of IDs as read
• webapp:
  • tests: only the frontend unit test is missing
• clean up: search for Wolle