activity: restore join requests activity

[arthyn]

Summary

As requested by @latter-bolden, this restores %activity handling group join requests as notifications and unreads, required for #5265.

Changes

• restored previous functionality for group asks

How did I test?

Sent ship a join request, saw unread marker increment, and received notification

Risks and impact

• Safe to rollback without consulting PR author? Yes
• Affects important code area:
  • [ ] Onboarding
  • [ ] State / providers
  • [ ] Message sync
  • [ ] Channel display
  • [X] Notifications
  • [ ] Other:

Rollback plan

Screenshots / videos

[jamesacklin]

@latter-bolden Are you planning to take the DNM label off and merge yourself?

[latter-bolden]

Yeah I'll usher it through, we don't want this to go out yet. We need the client that can clear these badges to be deployed before flipping them back on.

[latter-bolden]

Release pipeline wise, we're good to land this on develop now

@arthyn feel free to merge