A migration was added out-of-order, which meant that in clients who
had already run the migration after, it would be skip.
This commit re-adds the migration so it's run, tested against an empty
account and one that had already migrated.
* feat: Add seen/unseen activity center state
* feat: ActivityCenterState for grouping ActivityCenter unread messages cnt and seen state
* feat: always use messenger's addActivityCenterNotification & add state to the response
* Remove unused activity center endpoints form api and fix test
Andrea Maria Piana
Mikhail Rogachev
Samuel Hawksby-Robinson
Michele Balistreri
Vitaliy Vlasov