Major refactoring for easier tests

[sonroyaalmerol]

Context

• The current code does not allow for easy unit tests without integrating methods across different dependency modules. This makes it hard to diagnose problematic parts where an automated test can easily detect.

Choices

Test instructions

Checklist before requesting a review

• I have performed a self-review of my code
• I've added documentation about this change to the README.
• I've not introduced breaking changes.

[github-actions]

The Docker image for this pull request has been built and pushed to GHCR.

Image URL: ghcr.io/sonroyaalmerol/m3u-stream-merger-proxy:pr-218