Implements MSC2832 by sending application service access
tokens in the Authorization header.
The access token is also still sent as a query parameter until
the application service ecosystem has fully migrated to using
headers. In the future this could be made opt-in, or removed
completely.
* Update worker docs to remove group endpoints.
* Removes an unused parameter to `ApplicationService`.
* Break dependency between media repo and groups.
* Avoid copying `m.room.related_groups` state events during room upgrades.
David Robertson