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

Be able to test `/login/sso/redirect` in Complement

Spawning from
https://github.com/element-hq/sbg/pull/421#discussion_r1854926218 where
we have a proxy that intercepts responses to
`/_matrix/client/v3/login/sso/redirect(/{idpId})` in order to upgrade
them to use OAuth 2.0 Pushed Authorization Requests (PAR). We have some
Complement tests in that codebase that go over this flow and these
changes are required [in order for the URL's to line
up](https://github.com/element-hq/synapse/blob/d648c8ce3f4cbf61191b9f5302e405f7b0288677/synapse/rest/client/login.py#L652-L673).

MSC4115 has now completed FCP, so we can enable it by default and switch
to the stable identifier.

This is an alternative to
https://github.com/matrix-org/matrix-rust-sdk/issues/3340 where we don't
need to change our CI setup too much in the Rust SDK repository, and
still can test MSC3266.

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

MSC3967 was updated recently to make it more robust to network failures:

> there is an existing cross-signing master key and it exactly matches
the cross-signing master key provided in the request body. If there are
any additional keys provided in the request (self signing key, user
signing key) they MUST also match the existing keys stored on the
server. In other words, the request contains no new keys. If there are
new keys, UIA MUST be performed.


https://github.com/matrix-org/matrix-spec-proposals/blob/hughns/device-signing-upload-uia/proposals/3967-device-signing-upload-uia.md#proposal

This covers the case where the 200 OK is lost in transit so the client
retries the upload, only to then get UIA'd.

Complement tests: https://github.com/matrix-org/complement/pull/713 -
passing example
https://github.com/element-hq/synapse/actions/runs/7976948122/job/21778795094?pr=16943#step:7:8820

### Pull Request Checklist

<!-- Please read
https://element-hq.github.io/synapse/latest/development/contributing_guide.html
before submitting your pull request -->

* [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).
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.
- Feel free to credit yourself, by adding a sentence "Contributed by
@github_username." or "Contributed by [Your Name]." to the end of the
entry.
* [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: reivilibre <oliverw@matrix.org>

Remove experimental MSC2716 implementation to incrementally import history into existing rooms (#15748)

Context for why we're removing the implementation:

 - https://github.com/matrix-org/matrix-spec-proposals/pull/2716#issuecomment-1487441010
 - https://github.com/matrix-org/matrix-spec-proposals/pull/2716#issuecomment-1504262734

Anyone wanting to continue MSC2716, should also address these leftover tasks: https://github.com/matrix-org/synapse/issues/10737

Closes https://github.com/matrix-org/synapse/issues/10737 in the fact that it is not longer necessary to track those things.

* Enable Complement tests for Faster Remote Room Joins on worker-mode

* (dangerous) Add an override to allow Complement to use FRRJ under workers

* Newsfile

Signed-off-by: Olivier Wilkinson (reivilibre) <oliverw@matrix.org>

* Fix race where we didn't send out replication notification

* MORE HACKS

* Fix get_un_partial_stated_rooms_token to take instance_name

* Fix bad merge

* Remove warning

* Correctly advance un_partial_stated_room_stream

* Fix merge

* Add another notify_replication

* Fixups

* Create a separate ReplicationNotifier

* Fix test

* Fix portdb

* Create a separate ReplicationNotifier

* Fix test

* Fix portdb

* Fix presence test

* Newsfile

* Apply suggestions from code review

* Update changelog.d/14752.misc

Co-authored-by: Erik Johnston <erik@matrix.org>

* lint

Signed-off-by: Olivier Wilkinson (reivilibre) <oliverw@matrix.org>
Co-authored-by: Erik Johnston <erik@matrix.org>

Serving partial join responses is no longer experimental. They will only be served under the stable identifier if the the undocumented config flag experimental.msc3706_enabled is set to true.

Synapse continues to request a partial join only if the undocumented config flag experimental.faster_joins is set to true; this setting remains present and unaffected.

Fix https://github.com/matrix-org/synapse/issues/14390

 - Client API: `/_matrix/client/unstable/org.matrix.msc3030/rooms/<roomID>/timestamp_to_event?ts=<timestamp>&dir=<direction>` -> `/_matrix/client/v1/rooms/<roomID>/timestamp_to_event?ts=<timestamp>&dir=<direction>`
 - Federation API: `/_matrix/federation/unstable/org.matrix.msc3030/timestamp_to_event/<roomID>?ts=<timestamp>&dir=<direction>` -> `/_matrix/federation/v1/timestamp_to_event/<roomID>?ts=<timestamp>&dir=<direction>`

Complement test changes: https://github.com/matrix-org/complement/pull/559

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

Fix Complement `TestCanRegisterAdmin` with workers, by adding Complement's shared registration secret. (#12819)

Fixes matrix-org/complement#330 (or it will, once we remove the old files).

It's not quite a lift-and-shift: I've also taken the opportunity to get rid of the custom CA that we used to use to sign the TLS certs, which has been superceded by the CA exposed by Complement.