* Add identifier option to apache2_module
There is a convention connecting the name passed to a2enmod and the one
appearing in apache2ctl -M. Not all modules follow this convention and
we have added a growing list of implicit conversions.
As a better long-term solution this adds an "identifier" option to be
able to set both strings explicitly.
* Run debian-specific tests only there
* Improve cleanup after apache2 tests
This is a follow-up/extension of https://github.com/ansible/ansible/pull/33630
* Add example for the new identifier option
* Put all debian tests in a block
