This is largely a precursor for the removal of the bundled webclient. The idea
is to present a page at / which reassures people that something is working, and
to give them some links for next steps.

The welcome page lives at `/_matrix/static/`, so is enabled alongside the other
`static` resources (which, in practice, means the client API is enabled). We'll
redirect to it from `/` if we have nothing better to display there.

It would be nice to have a way to disable it (in the same way that you might
disable the nginx welcome page), but I can't really think of a good way to do
that without a load of ickiness.

It's based on the work done by @krombel for #2601.

Notes on upgrading to python3, and README updates.

Remove obsolete settings from docker homeserver.yaml

These aren't used, because we have a `log_config` setting.

Use labels to tag builds with their SHA1 version.

Replace mentions of Vector with Riot

This is useful for homeservers not intended for users, such as bot-only homeservers or ones that only process IoT data.

* Add note to UPGRADE.rst about removing riot.im from list of trusted identity servers

Signed-off-by: Aaron Raimist <aaron@raim.ist>

* Add changelog

Signed-off-by: Aaron Raimist <aaron@raim.ist>

This is a bit of a half-assed effort at fixing https://github.com/matrix-org/synapse/issues/4252. Fundamentally the right answer is to drop support for Python 2.

Drop sent_transactions

Fix removing pushers on python 3

Add a basic .editorconfig

This should fix some "Starting db connection from sentinel context" warnings,
and will mean we get metrics for these processes.

Signed-off-by: Aaron Raimist <aaron@raim.ist>

It turns out that we accept events with non-ascii IDs, which would later cause
an explosion during state res.

Fixes #4226

Signed-off-by: Aaron Raimist <aaron@raim.ist>

Signed-off-by: Aaron Raimist <aaron@raim.ist>

* Fix auto join failures for servers that require user consent

* Fix auto join failures for servers that require user consent

* fix transaction wrapping bug that caused get_user_id_by_threepid_txn to fail

* towncrier

* white space

* Clean up the CSS for the fallback login form

I was finding this hard to work with, so simplify a bunch of things. Each
flow is now a form inside a div of class login_flow.

The login_flow class now has a fixed width, as that looks much better than each
flow having a differnt width.

* Support m.login.sso

MSC1721 renames m.login.cas to m.login.sso. This implements the change
(retaining support for m.login.cas for older clients).

* changelog

* Add better diagnostics to flakey keyring test

* fix interpolation fail

* Check logcontexts before and after each test

* update changelog

* update changelog

* Some words about garbage collections and logcontexts

* Do a GC after each test to fix logcontext leaks

This feels like an awful hack, but...

* changelog

Ignore __pycache__ directories in schema delta dir

Now that we use py3, compiled python ends up in __pycache__ rather than *.pyc.

https://github.com/vector-im/vector-web/issues/1977 --> https://github.com/vector-im/riot-web/issues/1977
And mention of Vector as a client replaced with Riot.

Fix some logcontext leaks

Features
--------

- Include flags to optionally add `m.login.terms` to the registration flow when consent tracking is enabled.
([\#4004](https://github.com/matrix-org/synapse/issues/4004), [\#4133](https://github.com/matrix-org/synapse/issues/4133),
[\#4142](https://github.com/matrix-org/synapse/issues/4142), [\#4184](https://github.com/matrix-org/synapse/issues/4184))
- Support for replacing rooms with new ones ([\#4091](https://github.com/matrix-org/synapse/issues/4091), [\#4099](https://github.com/matrix-org/synapse/issues/4099),
[\#4100](https://github.com/matrix-org/synapse/issues/4100), [\#4101](https://github.com/matrix-org/synapse/issues/4101))

Bugfixes
--------

- Fix exceptions when using the email mailer on Python 3. ([\#4095](https://github.com/matrix-org/synapse/issues/4095))
- Fix e2e key backup with more than 9 backup versions ([\#4113](https://github.com/matrix-org/synapse/issues/4113))
- Searches that request profile info now no longer fail with a 500. ([\#4122](https://github.com/matrix-org/synapse/issues/4122))
- fix return code of empty key backups ([\#4123](https://github.com/matrix-org/synapse/issues/4123))
- If the typing stream ID goes backwards (as on a worker when the master restarts), the worker's typing handler will no longer erroneously report rooms containing new
typing events. ([\#4127](https://github.com/matrix-org/synapse/issues/4127))
- Fix table lock of device_lists_remote_cache which could freeze the application ([\#4132](https://github.com/matrix-org/synapse/issues/4132))
- Fix exception when using state res v2 algorithm ([\#4135](https://github.com/matrix-org/synapse/issues/4135))
- Generating the user consent URI no longer fails on Python 3. ([\#4140](https://github.com/matrix-org/synapse/issues/4140),
[\#4163](https://github.com/matrix-org/synapse/issues/4163))
- Loading URL previews from the DB cache on Postgres will no longer cause Unicode type errors when responding to the request, and URL previews will no longer fail if
the remote server returns a Content-Type header with the chartype in quotes. ([\#4157](https://github.com/matrix-org/synapse/issues/4157))
- The hash_password script now works on Python 3. ([\#4161](https://github.com/matrix-org/synapse/issues/4161))
- Fix noop checks when updating device keys, reducing spurious device list update notifications. ([\#4164](https://github.com/matrix-org/synapse/issues/4164))

Deprecations and Removals
-------------------------

- The disused and un-specced identicon generator has been removed. ([\#4106](https://github.com/matrix-org/synapse/issues/4106))
- The obsolete and non-functional /pull federation endpoint has been removed. ([\#4118](https://github.com/matrix-org/synapse/issues/4118))
- The deprecated v1 key exchange endpoints have been removed. ([\#4119](https://github.com/matrix-org/synapse/issues/4119))
- Synapse will no longer fetch keys using the fallback deprecated v1 key exchange method and will now always use v2.
([\#4120](https://github.com/matrix-org/synapse/issues/4120))

Internal Changes
----------------

- Fix build of Docker image with docker-compose ([\#3778](https://github.com/matrix-org/synapse/issues/3778))
- Delete unreferenced state groups during history purge ([\#4006](https://github.com/matrix-org/synapse/issues/4006))
- The "Received rdata" log messages on workers is now logged at DEBUG, not INFO. ([\#4108](https://github.com/matrix-org/synapse/issues/4108))
- Reduce replication traffic for device lists ([\#4109](https://github.com/matrix-org/synapse/issues/4109))
- Fix `synapse_replication_tcp_protocol_*_commands` metric label to be full command name, rather than just the first character
([\#4110](https://github.com/matrix-org/synapse/issues/4110))
- Log some bits about room creation ([\#4121](https://github.com/matrix-org/synapse/issues/4121))
- Fix `tox` failure on old systems ([\#4124](https://github.com/matrix-org/synapse/issues/4124))
- Add STATE_V2_TEST room version ([\#4128](https://github.com/matrix-org/synapse/issues/4128))
- Clean up event accesses and tests ([\#4137](https://github.com/matrix-org/synapse/issues/4137))
- The default logging config will now set an explicit log file encoding of UTF-8. ([\#4138](https://github.com/matrix-org/synapse/issues/4138))
- Add helpers functions for getting prev and auth events of an event ([\#4139](https://github.com/matrix-org/synapse/issues/4139))
- Add some tests for the HTTP pusher. ([\#4149](https://github.com/matrix-org/synapse/issues/4149))
- add purge_history.sh and purge_remote_media.sh scripts to contrib/ ([\#4155](https://github.com/matrix-org/synapse/issues/4155))
- HTTP tests have been refactored to contain less boilerplate. ([\#4156](https://github.com/matrix-org/synapse/issues/4156))
- Drop incoming events from federation for unknown rooms ([\#4165](https://github.com/matrix-org/synapse/issues/4165))