Specifically, previously, each MUC would be added as a roster item, and
then each join presence would be counted as a resource of that item,
triggering 1 to 5 events and more backend logic in slixmpp.
As a result, joining big rooms is tremendously slow, (JID() calls,
event() calls, __getitem__ calls for nothing), and takes RAM (a quick
tracemalloc tells me around 1 MiB for 3500 participants, i.e. 2 big IRC
rooms). Those resources may not necessarily be cleaned properly, leading
to memory leaks on long-term usage.
This is a micro-optimization that adds an attribute to roster items so
that MUC room events can be ignored safely while not affecting common
roster usage.
The "message" event only receives messages with a body, and error
messages don’t necessarily have it. Removing the body requirement from
the "message" event could lean to unhandled conditions in existing code.
Scheduled events, connection, TLS handshake (with STARTTLS), read and write
on the socket are all done using only asyncio.
A lot of threads, and thread-related (and thus useless) things still remain.
This is only a first step.
