mod_bookmarks2: Advertise XEP-0049 support In the case mod_private isn’t loaded, some clients (like poezio) won’t even attempt to use Private XML Storage unless this feature is advertised. This is on the domain JID and not on the account JID!

This module writes out a traceback to `traceback.txt` in Prosodys data
directory (see `prosodyctl about`) when the signal `SIGUSR1` is
received. This is useful when debugging seemingly frozen instances in
case it is stuck in Lua code.