mod_firewall: spam-blocking.pfw: Remove requirement for invites to have no body Some clients (e.g. Gajim) send a body, which I guess makes sense. The bare JID sender check should already make it hard to bypass this (i.e. a normal client putting muc#user into a normal chat message shouldn't bypass the usual message filters).

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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.