Makes it so that groups/communities no longer exist from a user-POV. E.g. we remove:

* All API endpoints (including Client-Server, Server-Server, and admin).
* Documented configuration options (and the experimental flag, which is now unused).
* Special handling during room upgrades.
* The `groups` section of the `/sync` response.

Signed-off-by: David Teller <davidt@element.io>

Signed-off-by: jesopo <github@lolnerd.net>

Add a unique index to `state_group_edges` to prevent duplicates being accidentally introduced and the consequential impact to performance. (#12687)

Signed-off-by: Sami Olmari <sami@olmari.fi>

docbook doesn't auto-linkify links

Signed-off-by: Sean Quah <seanq@matrix.org>

Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>

* Update openid.md

Newer versions of keycloak returning a 404 when using the `/auth` prefix.

Related: https://github.com/matrix-org/synapse/issues/12714

Co-authored-by: Matthew Hodgson <matthew@matrix.org>

Add the `update_user_directory_from_worker` configuration option (superseding `update_user_directory`) to allow a generic worker to be designated as the worker to update the user directory. (#12654)

Co-authored-by: Shay <hillerys@element.io>

Add the `notify_appservices_from_worker` configuration option (superseding `notify_appservices`) to allow a generic worker to be designated as the worker to send traffic to Application Services. (#12452)

* Add mau_appservice_trial_days

* Add a test

* Tweaks

* changelog

* Ensure we sync after the delay

* Fix types

* Add config statement

* Fix test

* Reinstate logging that got removed

* Fix feature name

* `m.login.jwt`, which was never specced and has been deprecated
  since Synapse 1.16.0. (`org.matrix.login.jwt` can be used instead.)
* `uk.half-shot.msc2778.login.application_service`, which was
  stabilized as part of the Matrix spec v1.2 release.

Don't log stack traces for cancelled requests and use a custom HTTP
status code of 499.

Signed-off-by: Sean Quah <seanq@element.io>

This was originally added when we first added a `MemoryHandler` to the default
log config back in https://github.com/matrix-org/synapse/pull/8040, to ensure
that we didn't explode with an infinite loop if there was an error formatting
the logs.

Since then, we made additional improvements to logging which make this
workaround redundant. In particular:

 * we no longer attempt to log un-UTF8-decodable byte sequences, which were the
   most likely cause of an error in the first place.

 * https://github.com/matrix-org/synapse/pull/8268 ensures that in the unlikely
   case that there *is* an error, it won't cause an infinite loop.

* Update config_documentation.md

Signed-off-by: Sami Olmari <sami@olmari.fi>

Signed-off-by: Ville Petteri Huh