mod_muc_moderation: Stamp XEP-0421 occupant-id for the acting moderator Gives clients some hint about which moderator it was who did the deed. The @by attribute does have the nick of the actor, but they could change their nickname at some point, which is what occupant-id solves. Ref #1816

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summary: Log a message once per minute
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This module sends `-- MARK --` to the log once per minute. This may be
useful to give a sense of how busy the server is or see that logging and
timers are still working.