[FEATURE] Support configuration directory for thanos::user (or other)

[Nuno09]

Is your feature request related to a problem? Please describe.
I am running thanos services with the prometheus user (RHEL/CentOS OS). But I have an issue with the thanos config dir always owned by 'root'. I don't understand why, is there a reason behind this?

Describe the solution you'd like
Support to set the 'config_dir' owner to the user running thanos.

Describe alternatives you've considered
I don't see any

Additional context
Here is the exact place this is done:

puppet-thanos/manifests/install.pp

Line 128 in a59248a

file { $config_dir:

[Nuno09]

I have a proposed PR: #54