Allow per-movie Default Audio Track Selection by admin

As I mentioned in my previous post:

I would like to be able to choose a different audio track for a specific movie, regardless of the user’s default language settings. For example, if I have The Passion of the Christ (2004) in my library and the video has 3 audio tracks: 1. Aramaic, 2. Spanish, 3. English — I want Plex to play track 1 (Aramaic) by default for this movie, even if the user’s default language is Spanish for all other content.