Unit tests - finalization

[metalwarrior665]

Implement unit tests (or update current ones) that will

1. Test all parsers. This might require doing some refactor, ideally the code is as clean that we only parse data coming from the website once (e.g. part of HTML or JSON -> part of dataset item). These should test against exact values as coming from the website, not just schema.
2. Test internal transformations - e.g. parsing from URL, categorizing inputs/URLs

Our OKR is to cover 80% use-cases but let's try to get closer to 100% :)

More details on how we want to structure tests: https://www.notion.so/apify/Tests-revamp-2024-Q1-2-b411bbfbf7e74af6a5f24fb36fe68332