Three messages that were implemented and only encoder-tested: a member
giving up their own membership (136), an owner disbanding the room and
freeing its name (137), and a privileged account handing time to another
user (123), which the recipient then sees as privilege time of their own.
UserJoinedRoom and UserLeftRoom (codes 16 and 17) were parsed and applied
to the roster with nothing proving either end of that, which is the kind
of gap that only shows up when someone relies on it.