Get original language for both videos and subtitles

[BinaryQuantumSoul]

Is your feature request related to a problem? Please describe.
I need to be able to search videos filtered by original video language.
I also need to get the original subtitles, but getByLanguage requires a language and I don't know which is the original.

Describe the solution you'd like
Two possibilities for both cases:

• Best would be a SearchFilter with language to be used in search endpoint
• Other option could be to add a Language attribute in the Video class
• This attribute could be used in getByLanguage to get original track
• Other option could be a getOriginal method in ClosedCaptionManifest class

Describe alternatives you've considered
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How should this be implemented
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Additional context
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