compat: introduce apkg compat level

in order to allow config file changes without disruption in the future.

Fixes: #48
4 jobs for compat in 4 minutes and 30 seconds (queued for 5 seconds)
Status Job ID Name Coverage
  Test
passed #536988
flake8

00:03:13

passed #536989
pylint

00:03:34

passed #536991
self

00:03:39

passed #536990
unit

00:04:29