Augment Tmdb tags to include original language

[bradbeattie]

Changes
When generating tag metadata from TMDB, include the original language as a tag (e.g. lang-en or lang-fr).

The intent here is to piggyback on SqliteItemRepository's use of tags to determine item similarity to also consider a movie's original (primary) language. The result being that Jellyfin's "More Like This" would give some relevance to a movie's language.

Furthermore, in concert with #8842 this change would allow searching for content by language.

Issues

Partially addresses https://features.jellyfin.org/posts/39/filter-videos-by-audio-stream-language

[Shadowghost]

IMHO this is a workaround. Ideally current and original content language would be saved explicitly in the database.

[bradbeattie]

Yep. Happy to close if less patchy way of doing this is in the works.