Content API does not return data in user's preferred language by default

[SabreCat]

According to the documentation for GET /api/v3/content, if user authentication is provided but no language parameter is specified, the endpoint should return information in the user's preferred language. This doesn't appear to be the case, however -- if you don't include a language param in the request, it always returns English, even when supplying headers or session for a user with a different preferences.language set.

[MrJellyB]

Hi @SabreCat can I take this?

[CuriousMagpie]

@MrJellyB I've assigned this to you.