Provide ad-hoc interfaces for the export plugin

So we have direct API on how to integrate export jobs into the different
applications.
2 jobs for !45 with work/adhoc-export in 50 seconds (queued for 5 seconds)
latest detached
Status Name Job ID Coverage
  Build
passed freebsd_qt515 #159892
FreeBSD

00:00:42

passed suse_tumbleweed_qt515 #159891
Linux

00:00:43