Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

See the updated MSC2965

---------

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

Implementation of
[MSC4133](https://github.com/matrix-org/matrix-spec-proposals/pull/4133)
to support custom profile fields. It is behind an experimental flag and
includes tests.


### Pull Request Checklist

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---------

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

Otherwise these can race with other long running queries and lock out
all other queries.

This caused problems in v1.22.0 as we added an index to `events` table
in #17948, but that got interrupted and so next time we ran the
background update we needed to delete the half-finished index. However,
that got blocked behind some long running queries and then locked other
queries out (stopping workers from even starting).

It's possible to run into `SynapseError: 429 - Too Many Requests (rc_invites.per_issuer)`

`rc_invites.per_issuer` originally introduced in
https://github.com/matrix-org/synapse/pull/13125

This is particularly a problem in a state reset scenario where the membership
might change without a corresponding event.

This PR is targeting a scenario where a state reset happens which causes
room membership to change. Previously, the cache would just hold onto
stale data and now we properly bust the cache in this scenario.

We have a few tests for these scenarios which you can see are now fixed
because we can remove the `FIXME` where we were previously manually
busting the cache in the test itself.

This is a general Synapse thing so by it's nature it helps out Sliding
Sync.

Fix https://github.com/element-hq/synapse/issues/17368

Prerequisite for https://github.com/element-hq/synapse/issues/17929

---

Match when are busting `_curr_state_delta_stream_cache`

Adds a query param `type` to `/_synapse/admin/v1/rooms/{room_id}/state`
that filters the state event query by state event type.

---------

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

It's been rotated out of known clients, and should be safe for removal
now.

Fixes https://github.com/element-hq/synapse/issues/17373

### Pull Request Checklist

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file](https://element-hq.github.io/synapse/latest/development/contributing_guide.html#changelog).
The entry should:
- Be a short description of your change which makes sense to users.
"Fixed a bug that prevented receiving messages from other servers."
instead of "Moved X method from `EventStore` to `EventWorkerStore`.".
  - Use markdown where necessary, mostly for `code blocks`.
  - End with either a period (.) or an exclamation mark (!).
  - Start with a capital letter.
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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Currently purging a complex room can lead to a lot of orphaned rows left
behind in the state groups tables.
It seems it is because we are loosing track of state groups sometimes.

This change uses the `room_id` indexed column of `state_groups` table to
decide what to delete instead of doing an indirection through
`event_to_state_groups`.

Related to https://github.com/element-hq/synapse/issues/3364.

### Pull Request Checklist

* [x] Pull request is based on the develop branch
* [x] Pull request includes a [changelog
file](https://element-hq.github.io/synapse/latest/development/contributing_guide.html#changelog).
* [x] [Code
style](https://element-hq.github.io/synapse/latest/code_style.html) is
correct
(run the
[linters](https://element-hq.github.io/synapse/latest/development/contributing_guide.html#run-the-linters)

)

---------

Co-authored-by: Erik Johnston <erikj@jki.re>

Refactor `get_profile` to avoid returning "empty" (`None` / `null`)
fields. Currently this is not very important, but will be more useful
once #17488 lands. It does update the servlet to use this now which has
a minor change in behavior: additional fields served over federation
will now be properly sent back to clients.

It also adds constants for `avatar_url` / `displayname` although I did
not attempt to use it everywhere possible.

Add a test to verify remote user messages can be redacted via admin api redaction endpoint if requester is admin in room (#18043)

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>