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, 29 insertions, 0 deletions

diff --git a/synapse/http/servlet.py b/synapse/http/servlet.py
index 91ba93372c..6dd9b9ad03 100644
--- a/synapse/http/servlet.py
+++ b/synapse/http/servlet.py
@@ -79,6 +79,35 @@ def parse_integer(
     return parse_integer_from_args(args, name, default, required)
 
 
+@overload
+def parse_integer_from_args(
+    args: Mapping[bytes, Sequence[bytes]],
+    name: str,
+    default: Optional[int] = None,
+) -> Optional[int]:
+    ...
+
+
+@overload
+def parse_integer_from_args(
+    args: Mapping[bytes, Sequence[bytes]],
+    name: str,
+    *,
+    required: Literal[True],
+) -> int:
+    ...
+
+
+@overload
+def parse_integer_from_args(
+    args: Mapping[bytes, Sequence[bytes]],
+    name: str,
+    default: Optional[int] = None,
+    required: bool = False,
+) -> Optional[int]:
+    ...
+
+
 def parse_integer_from_args(
     args: Mapping[bytes, Sequence[bytes]],
     name: str,