* Add tests

* Ensure deleted statuses are marked as such

* Save some redis memory by not storing URIs in delete_upon_arrival values

* Avoid possible race condition when processing incoming Deletes

* Avoid potential duplicate Delete forwards

* Lower lock durations to reduce issues in case of hard crash of the Rails process

* Check for `lock.aquired?` and improve comment

* Refactor RedisLock usage in app/lib/activitypub

* Fix using incorrect or non-existent sender for relaying Deletes

* Avoid sending explicit Undo->Announce when original deleted

* Do not forward a reply back to the server that sent it

* Deduplicate inboxes of rebloggers' followers for delete forwarding

* Adjust test

* Fix wrong class, bad SQL, wrong variable, outdated comment

* Decouple Status#local? from uri being nil

* Replace on-the-fly URI generation with stored URIs

- Generate URI in after_save hook for local statuses
- Use static value in TagManager when available, fallback to tag format
- Make TagManager use ActivityPub::TagManager to understand new format
- Adjust tests

* Use other heuristic for locality of old statuses, do not perform long query

* Exclude tombstone stream entries from Atom feed

* Prevent nil statuses from landing in Pubsubhubbub::DistributionWorker

* Fix URI not being saved (#4818)

* Add more specs for Status

* Save generated uri immediately

and also fix method order to minimize diff.

* Fix alternate HTML URL in Atom

* Fix tests

* Remove not-null constraint from statuses migration to speed it up

* Forward ActivityPub creates that reply to local statuses

* Fix test

* Fix wrong signers

* Add ActivityPub inbox

* Handle ActivityPub deletes

* Handle ActivityPub creates

* Handle ActivityPub announces

* Stubs for handling all activities that need to be handled

* Add ActivityPub actor resolving

* Handle conversation URI passing in ActivityPub

* Handle content language in ActivityPub

* Send accept header when fetching actor, handle JSON parse errors

* Test for ActivityPub::FetchRemoteAccountService

* Handle public key and icon/image when embedded/as array/as resolvable URI

* Implement ActivityPub::FetchRemoteStatusService

* Add stubs for more interactions

* Undo activities implemented

* Handle out of order activities

* Hook up ActivityPub to ResolveRemoteAccountService, handle
Update Account activities

* Add fragment IDs to all transient activity serializers

* Add tests and fixes

* Add stubs for missing tests

* Add more tests

* Add more tests