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

Signed-off-by: Dirk Klimpel <dirk@klimpel.org>

* Recommend poetry in docs

- readme
- contributor guide
- upgrade notes
- new dev cheat sheet for poetry

Co-authored-by: Shay <hillerys@element.io>
Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>

* Background workers aren't experimental anymore

* Newsfile

Signed-off-by: Olivier Wilkinson (reivilibre) <oliverw@matrix.org>

* Stream writers aren't experimental either

This disables the endpoints (and sync response fields) for
groups/communities by default.

As discussed at https://github.com/matrix-org/synapse/pull/12179#discussion_r837263852

And update the upgrade notes to point at old versions of the documentation.

Switching to a sequence means there's no need to track `last_txn` on the
AS state table to generate new TXN IDs. This also means that there is
no longer contention between the AS scheduler and AS handler on updates
to the `application_services_state` table, which will prevent serialization
errors during the complete AS txn transaction.

Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>
Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

Flesh out documentation for running SyTest against Synapse, including use of Postgres and worker mode. (#12271)

Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>

HAproxy reverse proxy guide update to stop sending IPv4-mapped address to HS.