I still don't understand why it increased the size of the firewall logs
by a factor of 5 to 10, but we don't really need structured logs from
systemd-journald and the author seems to discourage it's use, so I will
not investigate further.
A call to sendLogsToRemote for logs received through RELP/UDP has
been added (to send them to Logstash/Redis/…), so common.conf's prefix
must be lower than collector.conf's.
Note: future "third-party" config files will also call sendLogsToRemote
and thus will also have to use a prefix higher than 10.