Move on from puppet6

[zilchms]

So, this module needs a few things to bring it up to standard. As puppet6 is EOL, puppet7 being the default standard right now and puppet8 release just happened, this module needs to migrate upwards.

Steps:

• First enable puppet7 support additionally to puppet6 (migration version)
• Then drop support for puppet6
• Then maybe add support for puppet8

bastelfreak did some things with modulesync here:
#139 and #160 but the CI seems to not like any of it; #139 CI run is too old to have logs, so we might want to rerun the workflow or open a new PR