Implement client configs

[jkroepke]

What this PR does / why we need it

Which issue this PR fixes

(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #

• fixes #

Special notes for your reviewer

Particularly user-facing changes

Checklist

Complete these before marking the PR as ready to review:

• DCO signed
• The PR title has a summary of the changes
• The PR body has a summary to reflect any significant (and particularly user-facing) changes introduced by this PR

[codecov]

Codecov Report

Attention: Patch coverage is 78.26087% with 20 lines in your changes missing coverage. Please review.

Project coverage is 83.07%. Comparing base (b9bba17) to head (639c569).

Files with missing lines	Patch %	Lines
internal/config/validate.go	10.00%	6 Missing and 3 partials ⚠️
internal/openvpn/callbacks.go	75.75%	6 Missing and 2 partials ⚠️
cmd/daemon/root.go	62.50%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #383      +/-   ##
==========================================
- Coverage   83.15%   83.07%   -0.09%     
==========================================
  Files          50       50              
  Lines        2856     2913      +57     
==========================================
+ Hits         2375     2420      +45     
- Misses        367      375       +8     
- Partials      114      118       +4     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.