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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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
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---------

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>

`defer.returnValue` was only needed in Python 2; in Python 3, a simple
`return` is fine.

`twisted.internet.defer.returnValue` is deprecated as of Twisted 24.7.0.

Most uses of `returnValue` in synapse were removed a while back; this
cleans up some remaining bits.

This is essentially matrix-org/synapse#14392. I didn't see anything in
there about updating sytest or complement.

The main driver of this is so that I can use `jsonb_path_exists` in
#17488. 

This is already done for `purge_history` but seems to have been
forgotten for `purge_room`.

Update reverse proxy docs with what we've learned from
https://github.com/element-hq/synapse/pull/17986

Also vice versa and update our nginx config with what I learned from the
reverse proxy docs.

### Pull Request Checklist

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The entry should:
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"Fixed a bug that prevented receiving messages from other servers."
instead of "Moved X method from `EventStore` to `EventWorkerStore`.".
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  - End with either a period (.) or an exclamation mark (!).
  - Start with a capital letter.
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Fixes various `mypy` errors associated with Twisted `24.11.0`.

Hopefully addresses https://github.com/element-hq/synapse/issues/17075,
though I've yet to test against `trunk`.

Changes should be compatible with our currently pinned Twisted version
of `24.7.0`.

As I found the current docstrings a bit unclear while trying to wrap my
head around this class.

Supersedes https://github.com/element-hq/synapse/pull/17958.

Awkwardly, the changes made to fix the mypy errors in 1.12.1 cause
errors in 1.11.2. So you'll need to update your mypy version to 1.12.1
to eliminate typechecking errors during developing.

The existing `email.smtp_host` config option is used for two distinct
purposes: it is resolved into the IP address to connect to, and used to
(request via SNI and) validate the server's certificate if TLS is
enabled. This new option allows specifying a different name for the
second purpose.

This is especially helpful, if `email.smtp_host` isn't a global FQDN,
but something that resolves only locally (e.g. "localhost" to connect
through the loopback interface, or some other internally routed name),
that one cannot get a valid certificate for.
Alternatives would of course be to specify a global FQDN as
`email.smtp_host`, or to disable TLS entirely, both of which might be
undesirable, depending on the SMTP server configuration.

Another config option on my quest to a `*_path` variant for every
secret. This time it’s `macaroon_secret_key_path`.

Reading secrets from files has the security advantage of separating the secrets from the config. It also simplifies secrets management in Kubernetes. Also useful to NixOS users.

This section could probably do with a lot more editorial attention, but
for now this is all there is in terms of documentation. The field is
already returned by Synapse:
https://github.com/element-hq/synapse/blob/4587decd678300217969f1d2f69b226421a33ced/synapse/handlers/admin.py#L150

`last_seen_ts` was introduced in
https://github.com/matrix-org/synapse/pull/16218

- Fetch the number of invites the provided user has sent after a given
timestamp
- Fetch the number of rooms the provided user has joined after a given
timestamp, regardless if they have left/been banned from the rooms
subsequently
- Get report IDs of event reports where the provided user was the sender
of the reported event