And convert some inlineDeferreds to async-friendly functions.

Just a small change missed in 7950aa8a.

This PR removes a set that was created and [initially used](https://github.com/matrix-org/synapse/commit/1d2a0040cff8d04cdc7d7d09d8f04a5d628fa9dd#diff-0bc92da3d703202f5b9be2d3f845e375f5b1a6bc6ba61705a8af9be1121f5e42R435-R436), but is no longer today.

May help cut down a bit on the time it takes to accept invites.

Synapse 1.27.0rc2 (2021-02-11)
==============================

Features
--------

- Further improvements to the user experience of registration via single sign-on. ([\#9297](https://github.com/matrix-org/synapse/issues/9297))

Bugfixes
--------

- Fix ratelimiting introduced in v1.27.0rc1 for invites to respect the `ratelimit` flag on application services. ([\#9302](https://github.com/matrix-org/synapse/issues/9302))
- Do not automatically calculate `public_baseurl` since it can be wrong in some situations. Reverts behaviour introduced in v1.26.0. ([\#9313](https://github.com/matrix-org/synapse/issues/9313))

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

- Clarify the sample configuration for changes made to the template loading code. ([\#9310](https://github.com/matrix-org/synapse/issues/9310))

This breaks some people's configurations (if their Client-Server API
is not accessed via port 443).

This has the side-effect of being able to remove use of `inlineCallbacks`
in the test-cases for cleaner tracebacks.

Remove conflicting sqlite tables that throw sqlite3.OperationalError: object name reserved for internal use: event_search_content when running the twisted unit tests.

Fix #8996

Remove unneeded type constraints on 3rd party protocol lookup responses

* Adds type hints to the groups servlet and stringutils code.
* Assert the maximum length of some input values for spec compliance.

* Handle the case of lxml not finding a document tree.
* Parse the document encoding from the XML tag.

New API /_synapse/admin/rooms/{roomId}/context/{eventId}

Signed-off-by: Joseph Arnault <computerdude90042@outlook.com>

Signed-off-by: Dan Callahan <danc@element.io>

Co-authored-by: compu42 <56663749+compu42@users.noreply.github.com>

Fixes some exceptions if the room state isn't quite as expected.
If the expected state events aren't found, try to find them in the
historical room state. If they still aren't found, fallback to a reasonable,
although ugly, value.

This fixes the Jinja2 templates for the mapping provider.

* Adds proper dependencies.
* Minor fixes in database layer.

* fix validation and don't use built-in validation UI

Co-authored-by: Bruno Windels <brunow@element.io>

config: Add detail to auto_join_rooms comment

Signed-off-by: Gary Dykstra <gary@dykstranet.com>

Also add a few more IP ranges to the default blacklist.