Follow-up from "ADD ActivityPub blueprint" - expand on permissions for subscriptions

The following discussions from !131548 (merged) should be addressed:

• @tkuah started a discussion: (+8 comments)

  It is possible that this have some overlap with https://docs.gitlab.com/ee/architecture/blueprints/gitlab_events_platform/ /cc @grzesiek @fabiopitino @marshall007

  Depending on the status of each initiative, we may have to reconcile these two proposals, some options :

  • Work on ActivityPub, follow-up when GitLab Events Platform is ready
  • Work on GitLab events Platform where ActivityPub is first consumer
  • Work on GitLab events Platform first with another consumer

• @fabiopitino started a discussion: (+4 comments)

  @oelmekki how should we deal with permissions on the resource? Examples:

  • A user tries to subscribe to activities of a project that they have no access to.
  • A user subscribes to some project's activities while the project is public. Afterwards the project becomes private and the subscriber shouldn't receive any more events.

/cc @oelmekki @jpcyiza