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 1 second)
Status Job ID Name Coverage
  Test
passed #536992
flake8

00:03:14

passed #536993
pylint

00:03:37

passed #536995
self

00:03:42

passed #536994
unit

00:04:29