This is a boolean option. If set to `true` and some server's JID
is in user's roster, then messages from any user of this server are
accepted even if no subscription present.
The option is enabled by default.
Notice: The arguments expected have changed, instead of
muc_register_nick Tim email@example.com muc.example.org
it expects now:
muc_register_nick Tim firstname.lastname@example.org example.org
muc_unregister_nick email@example.com example.org
When a client enabled push notifications during the current session,
notifications should be suppressed as long as the client is online.
Suppressing the notification didn't work for the case where the
notification was triggered by MAM, but this is now fixed.