This became a problem because #foundation-office:matrix.org has a
malformed create event with its `predecessor` set to a string instead of
a map.
The solution to this is, unfortunately, to do more shotgun parsing to
extract only the desired fields rather than trying to parse the entire
content every time. To prevent this kind of problem from happening
again, `RoomCreateEventContent` must only be used for creating new PDUs,
existing PDUs must be shotgun-parsed.
This gets rid of 3 instances of re-parsing the room version.
There's one place where we need the event ID of the room create event to
verify federation responses, so now we just look up the event ID at that
point instead.
This will break backwards compatibility of configurations, but
ensures that a previously-configured setting won't get dropped
arbitrarily. Pretty much worth it, I think.
If all join requests to resident servers fail or if the joining server
is the only resident server (i.e. the room is local-only), we would
previously send a 500 error, even if the more correct response would be
M_UNAUTHORIZED (e.g. if the user tries to join an invite-only room).
To fix this, we now return the error generated by attempting the join
locally, which correctly informs the client about why their request
failed.
Fixes a set of bugs introduced by 00b77144c1,
where we replaced explicit `RoomVersionId` matches with `version < V11`
comparisons. The `Ord` impl on `RoomVersionId` does not work like that,
and is in fact a lexicographic string comparison[1]. The most visible
effect of these bugs is that incoming redaction events would sometimes
be ignored.
Instead of reverting to the explicit matches, which were quite verbose,
I implemented a `RoomVersion` struct that has flags for each property
that we care about. This is similar to the approach used by ruma[2] and
synapse[3].
[1]: 7cfa3be0c6/crates/ruma-common/src/identifiers/room_version_id.rs (L136)
[2]: 7cfa3be0c6/crates/ruma-state-res/src/room_version.rs
[3]: c856ae4724/synapse/api/room_versions.py
