Release 2.12.5-1

Note: The release builds for this security update were prepared in a private
fork before publishing the release and were uploaded from there:
https://git.icinga.com/packaging/icinga2-2.12.5-2.11.10/raspbian-icinga2
3 jobs for 2.12 in 133 minutes and 48 seconds (queued for 3 seconds)