* 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.

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

Resolves #10339

* Formally type the UserProfile in user searches
* export UserProfile in synapse.module_api
* Update docs

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

Fixes https://github.com/matrix-org/synapse/issues/12205

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

This includes the `typing`, `to_device`, `account_data`, `receipts`, and `presence`
streams (really anything except the `events` stream).

Remove workaround introduced in Synapse v1.50.0rc1 for Mjolnir compatibility. Breaks compatibility with Mjolnir v1.3.1 and earlier. (#11700)

Some stuff that came up while we were talking about #12173.

Add third_party module callbacks to check if a user can delete a room and deactivate a user (#12028)

* Add check_can_deactivate_user

* Add check_can_shutdown_rooms

* Documentation

* callbacks, not functions

* Various suggested tweaks

* Add tests for test_check_can_shutdown_room and test_check_can_deactivate_user

* Update check_can_deactivate_user to not take a Requester

* Fix check_can_shutdown_room docs

* Renegade and use `by_admin` instead of `admin_user_id`

* fix lint

* Update docs/modules/third_party_rules_callbacks.md

Co-authored-by: Brendan Abolivier <babolivier@matrix.org>

* Update docs/modules/third_party_rules_callbacks.md

Co-authored-by: Brendan Abolivier <babolivier@matrix.org>

* Update docs/modules/third_party_rules_callbacks.md

Co-authored-by: Brendan Abolivier <babolivier@matrix.org>

* Update docs/modules/third_party_rules_callbacks.md

Co-authored-by: Brendan Abolivier <babolivier@matrix.org>

Co-authored-by: Brendan Abolivier <babolivier@matrix.org>

* Rewrites the demo documentation to be clearer, accurate, and moves it to our documentation tree.
* Improvements to the demo scripts:
	* `clean.sh` now runs `stop.sh` first to avoid zombie processes.
	* Uses more modern Synapse configuration (and removes some obsolete configuration).
	* Consistently use the HTTP ports for server name, etc.
	* Remove the `demo/etc` directory and place everything into the `demo/808x` directories.