Merge tag 'v1.37.0rc1' into develop

Synapse 1.37.0rc1 (2021-06-24)
==============================

This release deprecates the current spam checker interface. See the [upgrade notes](https://matrix-org.github.io/synapse/develop/upgrade#deprecation-of-the-current-spam-checker-interface) for more information on how to update to the new generic module interface.

This release also removes support for fetching and renewing TLS certificates using the ACME v1 protocol, which has been fully decommissioned by Let's Encrypt on June 1st 2021. Admins previously using this feature should use a [reverse proxy](https://matrix-org.github.io/synapse/develop/reverse_proxy.html) to handle TLS termination, or use an external ACME client (such as [certbot](https://certbot.eff.org/)) to retrieve a certificate and key and provide them to Synapse using the `tls_certificate_path` and `tls_private_key_path` configuration settings.

Features
--------

- Implement "room knocking" as per [MSC2403](matrix-org/matrix-spec-proposals#2403). Contributed by @Sorunome and anoa. ([\#6739](#6739), [\#9359](#9359), [\#10167](#10167), [\#10212](#10212), [\#10227](#10227))
- Add experimental support for backfilling history into rooms ([MSC2716](matrix-org/matrix-spec-proposals#2716)). ([\#9247](#9247))
- Implement a generic interface for third-party plugin modules. ([\#10062](#10062), [\#10206](#10206))
- Implement config option `sso.update_profile_information` to sync SSO users' profile information with the identity provider each time they login. Currently only displayname is supported. ([\#10108](#10108))
- Ensure that errors during startup are written to the logs and the console. ([\#10191](#10191))

Bugfixes
--------

- Fix a bug introduced in Synapse v1.25.0 that prevented the `ip_range_whitelist` configuration option from working for federation and identity servers. Contributed by @mikure. ([\#10115](#10115))
- Remove a broken import line in Synapse's `admin_cmd` worker. Broke in Synapse v1.33.0. ([\#10154](#10154))
- Fix a bug introduced in Synapse v1.21.0 which could cause `/sync` to return immediately with an empty response. ([\#10157](#10157), [\#10158](#10158))
- Fix a minor bug in the response to `/_matrix/client/r0/user/{user}/openid/request_token` causing `expires_in` to be a float instead of an integer. Contributed by @lukaslihotzki. ([\#10175](#10175))
- Always require users to re-authenticate for dangerous operations: deactivating an account, modifying an account password, and adding 3PIDs. ([\#10184](#10184))
- Fix a bug introduced in Synpase v1.7.2 where remote server count metrics collection would be incorrectly delayed on startup. Found by @heftig. ([\#10195](#10195))
- Fix a bug introduced in Synapse v1.35.1 where an `allow` key of a `m.room.join_rules` event could be applied for incorrect room versions and configurations. ([\#10208](#10208))
- Fix performance regression in responding to user key requests over federation. Introduced in Synapse v1.34.0rc1. ([\#10221](#10221))

Improved Documentation
----------------------

- Add a new guide to decoding request logs. ([\#8436](#8436))
- Mention in the sample homeserver config that you may need to configure max upload size in your reverse proxy. Contributed by @aaronraimist. ([\#10122](#10122))
- Fix broken links in documentation. ([\#10180](#10180))
- Deploy a snapshot of the documentation website upon each new Synapse release. ([\#10198](#10198))

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

- The current spam checker interface is deprecated in favour of a new generic modules system. See the [upgrade notes](https://matrix-org.github.io/synapse/develop/upgrade#deprecation-of-the-current-spam-checker-interface) for more information on how to update to the new system. ([\#10062](#10062), [\#10210](#10210), [\#10238](#10238))
- Stop supporting the unstable spaces prefixes from MSC1772. ([\#10161](#10161))
- Remove Synapse's support for automatically fetching and renewing certificates using the ACME v1 protocol. This protocol has been fully turned off by Let's Encrypt for existing installations on June 1st 2021. Admins previously using this feature should use a [reverse proxy](https://matrix-org.github.io/synapse/develop/reverse_proxy.html) to handle TLS termination, or use an external ACME client (such as [certbot](https://certbot.eff.org/)) to retrieve a certificate and key and provide them to Synapse using the `tls_certificate_path` and `tls_private_key_path` configuration settings. ([\#10194](#10194))

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

- Update the database schema versioning to support gradual migration away from legacy tables. ([\#9933](#9933))
- Add type hints to the federation servlets. ([\#10080](#10080))
- Improve OpenTracing for event persistence. ([\#10134](#10134), [\#10193](#10193))
- Clean up the interface for injecting OpenTracing over HTTP. ([\#10143](#10143))
- Limit the number of in-flight `/keys/query` requests from a single device. ([\#10144](#10144))
- Refactor EventPersistenceQueue. ([\#10145](#10145))
- Document `SYNAPSE_TEST_LOG_LEVEL` to see the logger output when running tests. ([\#10148](#10148))
- Update the Complement build tags in GitHub Actions to test currently experimental features. ([\#10155](#10155))
- Add a `synapse_federation_soft_failed_events_total` metric to track how often events are soft failed. ([\#10156](#10156))
- Fetch the corresponding complement branch when performing CI. ([\#10160](#10160))
- Add some developer documentation about boolean columns in database schemas. ([\#10164](#10164))
- Add extra logging fields to better debug where events are being soft failed. ([\#10168](#10168))
- Add debug logging for when we enter and exit `Measure` blocks. ([\#10183](#10183))
- Improve comments in structured logging code. ([\#10188](#10188))
- Update [MSC3083](matrix-org/matrix-spec-proposals#3083) support with modifications from the MSC. ([\#10189](#10189))
- Remove redundant DNS lookup limiter. ([\#10190](#10190))
- Upgrade `black` linting tool to 21.6b0. ([\#10197](#10197))
- Expose OpenTracing trace id in response headers. ([\#10199](#10199))

Author: babolivier