* Make `get_auth_chain_ids` return a Set
It has a set internally, and a set is often useful where it gets used, so let's
avoid converting to an intermediate list.
* Minor refactors in `on_send_join_request`
A little bit of non-functional groundwork
* Implement MSC3706: partial state in /send_join response
* Fix losing incoming EDUs if debug logging enabled
Fixes#11889. Homeservers should only be affected if the
`synapse.8631_debug` logger was enabled for DEBUG mode.
I am not sure if this merits a bugfix release: I think the logging can
be disabled in config if anyone is affected? But it is still pretty bad.
Debug for #8631.
I'm having a hard time tracking down what's going wrong in that issue.
In the reported example, I could see server A sending federation traffic
to server B and all was well. Yet B reports out-of-sync device updates
from A.
I couldn't see what was _in_ the events being sent from A to B. So I
have added some crude logging to track
- when we have updates to send to a remote HS
- the edus we actually accumulate to send
- when a federation transaction includes a device list update edu
- when such an EDU is received
This is a bit of a sledgehammer.
MSC3030: https://github.com/matrix-org/matrix-doc/pull/3030
Client API endpoint. This will also go and fetch from the federation API endpoint if unable to find an event locally or we found an extremity with possibly a closer event we don't know about.
```
GET /_matrix/client/unstable/org.matrix.msc3030/rooms/<roomID>/timestamp_to_event?ts=<timestamp>&dir=<direction>
{
"event_id": ...
"origin_server_ts": ...
}
```
Federation API endpoint:
```
GET /_matrix/federation/unstable/org.matrix.msc3030/timestamp_to_event/<roomID>?ts=<timestamp>&dir=<direction>
{
"event_id": ...
"origin_server_ts": ...
}
```
Co-authored-by: Erik Johnston <erik@matrix.org>
