Refactor and test coverage increase

[codecov[bot]]

Codecov Report

Attention: 111 lines in your changes are missing coverage. Please review.

Comparison is base (727645b) 68.24% compared to head (dc6c70b) 83.58%.

Files	Patch %	Lines
pw-bordercontrol/cmd/bordercontrol/main.go	44.55%	54 Missing and 2 partials :warning:
pw-bordercontrol/lib/stunnel/stunnel.go	83.85%	24 Missing and 12 partials :warning:
...rdercontrol/lib/feedproxy/feedproxy_connections.go	84.82%	17 Missing :warning:
...-bordercontrol/lib/feedproxy/feedproxy_metadata.go	88.23%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #47 +/- ## =========================================== + Coverage 68.24% 83.58% +15.34% =========================================== Files 11 12 +1 Lines 1965 2145 +180 =========================================== + Hits 1341 1793 +452 + Misses 583 284 -299 - Partials 41 68 +27 ```

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