We recently had someone need to inject additional configuration into
`/.well-known/matrix/client` as described here:
22b245bbd1/docs/bigbluebutton.md (have-dimension-create-meetings-with-elements-video-call-button)

There may be other use cases as well.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1393

Learn more here: https://github.com/matrix-org/synapse/releases/tag/v1.47.1

There was also a 2.1.5 security release made today.
2.2.0 contains the same security fix + more.

Both make handling of Client-Server API v3-prefixed requests better.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1404

We had to remove UID/GID environment variables that we used to pass
to the Synapse container, because it was causing a problem after
https://github.com/matrix-org/synapse/pull/11209

We were using both `--user` and UID/GID environment variables until now.

1f196f59cb

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1403

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1397
and https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1399

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1397

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1397

2.1.3 fixes a security vulnerability, which allowed attackers to
circuimvent policy checks by sending HTTP requests with trailing slashes.

Learn more in the matrix-corporal changelog: https://github.com/devture/matrix-corporal/blob/master/CHANGELOG.md

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1401

https://github.com/mautrix/facebook/releases/tag/v0.3.2 says that this
version re-adds SQLite support.

Official support ends today (2021-11-11).
Synapse still supports v9.6, but we'd better force users to transition
to newer versions anyway.

Until now, we were leaving services "enabled"
(symlinks in /etc/systemd/system/multi-user.target.wants/).

We clean these up now. Broken symlinks may still exist in older
installations that enabled/disabled services. We're not taking care
to fix these up. It's just a cosmetic defect anyway.