And set the required attribute in a few places which will error if
a parameter is not provided.

Previously, we were using `content.chunk_id` to connect one
chunk to another. But these events can be from any `sender`
and we can't tell who should be able to send historical events.
We know we only want the application service to do it but these
events have the sender of a real historical message, not the
application service user ID as the sender. Other federated homeservers
also have no indicator which senders are an application service on
the originating homeserver.

So we want to auth all of the MSC2716 events via power_levels
and have them be sent by the application service with proper
PL levels in the room.

Synapse 1.39.0rc1 (2021-07-20)
==============================

The Third-Party Event Rules module interface has been deprecated in favour of the generic module interface introduced in Synapse v1.37.0. Support for the old interface is planned to be removed in September 2021. See the [upgrade notes](https://matrix-org.github.io/synapse/latest/upgrade.html#upgrading-to-v1390) for more information.

Features
--------

- Add the ability to override the account validity feature with a module. ([\#9884](https://github.com/matrix-org/synapse/issues/9884))
- The spaces summary API now returns any joinable rooms, not only rooms which are world-readable. ([\#10298](https://github.com/matrix-org/synapse/issues/10298), [\#10305](https://github.com/matrix-org/synapse/issues/10305))
- Add a new version of the R30 phone-home metric, which removes a false impression of retention given by the old R30 metric. ([\#10332](https://github.com/matrix-org/synapse/issues/10332), [\#10427](https://github.com/matrix-org/synapse/issues/10427))
- Allow providing credentials to `http_proxy`. ([\#10360](https://github.com/matrix-org/synapse/issues/10360))

Bugfixes
--------

- Fix error while dropping locks on shutdown. Introduced in v1.38.0. ([\#10433](https://github.com/matrix-org/synapse/issues/10433))
- Add base starting insertion event when no chunk ID is specified in the historical batch send API. ([\#10250](https://github.com/matrix-org/synapse/issues/10250))
- Fix historical batch send endpoint (MSC2716) rejecting batches with messages from multiple senders. ([\#10276](https://github.com/matrix-org/synapse/issues/10276))
- Fix purging rooms that other homeservers are still sending events for. Contributed by @ilmari. ([\#10317](https://github.com/matrix-org/synapse/issues/10317))
- Fix errors during backfill caused by previously purged redaction events. Contributed by Andreas Rammhold (@andir). ([\#10343](https://github.com/matrix-org/synapse/issues/10343))
- Fix the user directory becoming broken (and noisy errors being logged) when knocking and room statistics are in use. ([\#10344](https://github.com/matrix-org/synapse/issues/10344))
- Fix newly added `synapse_federation_server_oldest_inbound_pdu_in_staging` prometheus metric to measure age rather than timestamp. ([\#10355](https://github.com/matrix-org/synapse/issues/10355))
- Fix PostgreSQL sometimes using table scans for queries against `state_groups_state` table, taking a long time and a large amount of IO. ([\#10359](https://github.com/matrix-org/synapse/issues/10359))
- Fix `make_room_admin` failing for users that have left a private room. ([\#10367](https://github.com/matrix-org/synapse/issues/10367))
- Fix a number of logged errors caused by remote servers being down. ([\#10400](https://github.com/matrix-org/synapse/issues/10400), [\#10414](https://github.com/matrix-org/synapse/issues/10414))
- Responses from `/make_{join,leave,knock}` no longer include signatures, which will turn out to be invalid after events are returned to `/send_{join,leave,knock}`. ([\#10404](https://github.com/matrix-org/synapse/issues/10404))

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

- Updated installation dependencies for newer macOS versions and ARM Macs. Contributed by Luke Walsh. ([\#9971](https://github.com/matrix-org/synapse/issues/9971))
- Simplify structure of room admin API. ([\#10313](https://github.com/matrix-org/synapse/issues/10313))
- Refresh the logcontext dev documentation. ([\#10353](https://github.com/matrix-org/synapse/issues/10353)), ([\#10337](https://github.com/matrix-org/synapse/issues/10337))
- Add delegation example for caddy in the reverse proxy documentation. Contributed by @moritzdietz. ([\#10368](https://github.com/matrix-org/synapse/issues/10368))
- Fix and clarify some links in `docs` and `contrib`. ([\#10370](https://github.com/matrix-org/synapse/issues/10370)), ([\#10322](https://github.com/matrix-org/synapse/issues/10322)), ([\#10399](https://github.com/matrix-org/synapse/issues/10399))
- Make deprecation notice of the spam checker doc more obvious. ([\#10395](https://github.com/matrix-org/synapse/issues/10395))
- Add instructions on installing Debian packages for release candidates. ([\#10396](https://github.com/matrix-org/synapse/issues/10396))

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

- Remove functionality associated with the unused `room_stats_historical` and `user_stats_historical` tables. Contributed by @xmunoz. ([\#9721](https://github.com/matrix-org/synapse/issues/9721))
- The third-party event rules module interface is deprecated in favour of the generic module interface introduced in Synapse v1.37.0. See the [upgrade notes](https://matrix-org.github.io/synapse/latest/upgrade.html#upgrading-to-v1390) for more information. ([\#10386](https://github.com/matrix-org/synapse/issues/10386))

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

- Convert `room_depth.min_depth` column to a `BIGINT`. ([\#10289](https://github.com/matrix-org/synapse/issues/10289))
- Add tests to characterise the current behaviour of R30 phone-home metrics. ([\#10315](https://github.com/matrix-org/synapse/issues/10315))
- Rebuild event context and auth when processing specific results from `ThirdPartyEventRules` modules. ([\#10316](https://github.com/matrix-org/synapse/issues/10316))
- Minor change to the code that populates `user_daily_visits`. ([\#10324](https://github.com/matrix-org/synapse/issues/10324))
- Re-enable Sytests that were disabled for the 1.37.1 release. ([\#10345](https://github.com/matrix-org/synapse/issues/10345), [\#10357](https://github.com/matrix-org/synapse/issues/10357))
- Run `pyupgrade` on the codebase. ([\#10347](https://github.com/matrix-org/synapse/issues/10347), [\#10348](https://github.com/matrix-org/synapse/issues/10348))
- Switch `application_services_txns.txn_id` database column to `BIGINT`. ([\#10349](https://github.com/matrix-org/synapse/issues/10349))
- Convert internal type variable syntax to reflect wider ecosystem use. ([\#10350](https://github.com/matrix-org/synapse/issues/10350), [\#10380](https://github.com/matrix-org/synapse/issues/10380), [\#10381](https://github.com/matrix-org/synapse/issues/10381), [\#10382](https://github.com/matrix-org/synapse/issues/10382), [\#10418](https://github.com/matrix-org/synapse/issues/10418))
- Make the Github Actions workflow configuration more efficient. ([\#10383](https://github.com/matrix-org/synapse/issues/10383))
- Add type hints to `get_{domain,localpart}_from_id`. ([\#10385](https://github.com/matrix-org/synapse/issues/10385))
- When building Debian packages for prerelease versions, set the Section accordingly. ([\#10391](https://github.com/matrix-org/synapse/issues/10391))
- Add type hints and comments to event auth code. ([\#10393](https://github.com/matrix-org/synapse/issues/10393))
- Stagger sending of presence update to remote servers, reducing CPU spikes caused by starting many connections to remote servers at once. ([\#10398](https://github.com/matrix-org/synapse/issues/10398))
- Remove unused `events_by_room` code (tech debt). ([\#10421](https://github.com/matrix-org/synapse/issues/10421))
- Add a github actions job which records success of other jobs. ([\#10430](https://github.com/matrix-org/synapse/issues/10430))

This reverts commit 83f1ccfc.

Port the third-party event rules interface to the generic module interface introduced in v1.37.0

Follow-up to #10332.

Add a new version of the R30 phone-home metric, which removes a false impression of retention given by the old R30 metric (#10332)

Signed-off-by: Olivier Wilkinson (reivilibre) <olivier@librepush.net>

This PR is tantamount to running 
```
pyupgrade --py36-plus --keep-percent-format `find synapse/ -type f -name "*.py"`
```

Part of #9744

It looks like it was first used and introduced in https://github.com/matrix-org/synapse/commit/5130d80d79fe1f95ce03b8f1cfd4fbf0a32f5ac8#diff-8a4a36a7728107b2ccaff2cb405dbab229a1100fe50653a63d1aa9ac10ae45e8R305 but the 

But the usage was removed in https://github.com/matrix-org/synapse/commit/4c6a31cd6efa25be4c9f1b357e8f92065fac63eb#diff-8a4a36a7728107b2ccaff2cb405dbab229a1100fe50653a63d1aa9ac10ae45e8

This adds an API for third-party plugin modules to implement account validity, so they can provide this feature instead of Synapse. The module implementing the current behaviour for this feature can be found at https://github.com/matrix-org/synapse-email-account-validity.

To allow for a smooth transition between the current feature and the new module, hooks have been added to the existing account validity endpoints to allow their behaviours to be overridden by a module.

These signatures would end up invalid since the joining/leaving/knocking
server would modify the response before calling send_{join,leave,knock}.

The postgres statistics collector sometimes massively underestimates the
number of distinct state groups are in the `state_groups_state`, which
can cause postgres to use table scans for queries for multiple state
groups.

We fix this by manually setting `n_distinct` on the column.

Signed-off-by: Olivier Wilkinson (reivilibre) <olivier@librepush.net>

Our documentation has a history of using a document's name as a way to link to it, such as "See [workers.md]() for details". This makes sense when you're traversing a directory of files, but less sense when the files are abstracted away - as they are on the documentation website.

This PR changes the links to various documentation pages to something that fits better into the surrounding sentence, as you would when making any hyperlink on the web.

This is to help with performance, where trying to connect to thousands
of hosts at once can consume a lot of CPU (due to TLS etc).

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

By referring to awaitables instead of deferreds.

This is part of fixing #6116: we want to put RC debs into a different place than release debs, so reprepro has to be able to tell them apart.