Rename Activitypub to ActivityPub

* Move ApiController to Api/BaseController

* API controllers inherit from Api::BaseController

* Add coverage for various error cases in api/base controller

* Change ActivityPub paging to match spec. Clean up ActivityPub outbox changes.

* Fix code style and test failures for OutboxController.

* Attempt to fix CI errors.

* Clean up collapsible components

* Expose user Outboxes and AS2 representations of statuses

* Save work thus far.

* Fix bad merge.

* Save my work

* Clean up pagination.

* First test working.

* Add tests.

* Add Forbidden error template.

* Revert yarn.lock changes.

* Fix code style deviations and use localized instead of hardcoded English text.