Refactor language component and add primary language support to tvdb provider

[aasmoe]

Make the language parameter names more clear. Creates a unified method __make_tmdb_request.

It also adds two minor fixes: missing . in metadataProvider/utils.py and make a return value None in movies/router.py
If this looks fine I can adjust tvdb.py in the same way and add multi-language support.

[maxdorninger]

looks good! 🎉

[aasmoe]

Here it is!:)

[maxdorninger]

While this generally looks good, there are some things which need to be changed or further explained/documented.

1. Why was the language parameter renamed to original_language, this new name doesn't really make sense.
2. Also the multi language aspect of the TVDB provider doesn't really work? I mean that it still is always going to get the metadata in English.

I think it'd be better if this were 2 PRs, one for the refactoring of the TMDB provider and one for adding the language feature to the tvdb provider.

[maxdorninger]

I'm a bit confused on what the point of the original_language argument is in this function.
It will still get the English metadata from TVDB, right?

[aasmoe]

Since tvdb provider is still only making plain queries, yes you are right, it is not being used for searching and fetching metadata. Still it serves to add original language to the db record for the show/movie which is consistent with what we already do with tmdb.

[maxdorninger]

Suggested change

	if original_language:
	return self.__make_tmdb_request(
	endpoint=f"/tv/shows/{show_id}",
	original_language=original_language,
	context=f"get show metadata for ID {show_id}",
	)
	raise
	return initial_metadata
	if not original_language:
	return initial_metadata

[aasmoe]

Sorry for making the PR so broad.

1. Regarding renaming language to original_language and selected_language. When revisiting code, I was confused by the generic name "language". At first this value is captured from the search result when adding media, and then it is matched to primary_languages setting to check if it or default langauge should be used, hence -> selected_langauge. Until it is compared to the primary_languages setting, it is just the original language value being passed. Also it is stored in db as under original_language. I wanted to differentiate it. What do you think?
2. Yes you are right! No new language functionality is added to metadataproviders>tvdb.py... Currently tvdb provider always shows metadata in the original language? I think I tricked myself and searched for media in my primary languages to test, and I was satisfied when they were displayed as I expected, but it seems all results no matter what are displayed and fetched in original language.

Maybe that is might as well and this PR can be limited to refactoring. The multi language feature for tvdb can be done separately, or what do you think is best?