Add MSC3030 experimental client and federation API endpoints to get the closest event to a given timestamp (#9445)

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>

1 files changed, 3 insertions, 0 deletions

diff --git a/synapse/config/experimental.py b/synapse/config/experimental.py
index 8b098ad48d..d78a15097c 100644
--- a/synapse/config/experimental.py
+++ b/synapse/config/experimental.py
@@ -46,3 +46,6 @@ class ExperimentalConfig(Config):
 
         # MSC3266 (room summary api)
         self.msc3266_enabled: bool = experimental.get("msc3266_enabled", False)
+
+        # MSC3030 (Jump to date API endpoint)
+        self.msc3030_enabled: bool = experimental.get("msc3030_enabled", False)