Unit tests for sitemap extractor

[nikitachapovskii-dev]

We might want to create some unit tests so later they can be expanded

[nicklamonov]

This is in PR state.
Who this should be assigned to, @ruocco-l , @nikitachapovskii-dev ? :)

[ruocco-l]

This one specifically goes to @nikitachapovskii-dev , he already opened a PR on it (but it's currently blocked by this one from me