CheckForSoftFail returns true if the event should be soft-failed and false otherwise.

GetAuthEvents returns the numeric IDs for the auth events.

GetMembershipsAtState filters the state events to only keep the "m.room.member" events with a "join" membership.

IsServerCurrentlyInRoom checks if a server is in a given room, based on the room memberships.

TODO: Remove this when we have tests to assert correctness of this function.

Map from numeric event ID to event.