Make Coredns config configurable

[rwaffen]

• CoreDNS config map is exported to a template with a variable set for the path so that one can bring its own config map if desired.
• the template uses full qualified variable names, so that when the template path is changed one also can add more variables without touching the manifest and updating the variables hash of the template

[rwaffen]

i updated the PR to use hiera, i hope this is like you wanted it?

[ananace]

I'd personally prefer a hiera override, but with the main template still rendered in Puppet if there's no value provided from there - since that works better for ENC use-cases.

[rwaffen]

but when i set the hiera value in the module data, there will always be a value for this. wont it? or do i not understand this in the right way?

but you say i shall build it this way that we check for hiera, if empty we render the template?

[ananace]

What I meant with the ENC use-case is when you have an external node classifier directly providing the values - instead of setting them through Hiera, i.e. something that amounts to;

class { 'k8s':
  cluster_domain => 'example.com',
}

Hiera lookups won't find values set directly through puppet or an ENC;

$ cat example.pp 
class something (
  String[1] $value
) {
}

class { 'something':
  value => 'potatoes',
}

notice(lookup('something::value'))
$ puppet apply example.pp
Error: Function lookup() did not find a value for the name 'something::value'

[rwaffen]

ah okay, i don't use ENC very often and try to avoid it if i can. but now i understand you.

[ananace]

I still personally feel that a content parameter should be enough of a public API for configuring CoreDNS, template rendering is mostly class-internal complexity after all. But that's mainly just personal preference, and nothing that should prevent this from being merged if it's useful to people.