As opposed to only allowing the summary of spaces which the user is
already in or has world-readable visibility.
This makes the logic consistent with whether a space/room is returned
as part of a space and whether a space summary can start at a space.
If a room which the requesting user was invited to was queried over
federation it will now properly appear in the spaces summary (instead
of being stripped out by the requesting server).
Previously only world-readable rooms were shown. This means that
rooms which are public, knockable, or invite-only with a pending invitation,
are included in a space summary. It also applies the same logic to
the experimental room version from MSC3083 -- if a user has access
to the proper allowed rooms then it is shown in the spaces summary.
This change is made per MSC3173 allowing stripped state of a room to
be shown to any potential room joiner.
This could cause a minor data leak if someone defined a non-restricted join rule
with an allow key or used a restricted join rule in an older room version, but this is
unlikely.
Additionally this starts adding unit tests to the spaces summary handler.
This should help ensure that equivalent results are achieved between
homeservers querying for the summary of a space.
This implements modified MSC1772 rules, according to MSC2946.
The different is that the origin_server_ts of the m.room.create event
is not used as a tie-breaker since this might not be known if the
homeserver is not part of the room.
