text: Title: Revamp things-advanced (WSGI/ASGI) examples
  Body: We ought to showcase media handling in these instead of manually wrangling (de-)serialization. It is fine to show what is possible, but the emphasis should still be on media.
  
  Revise App vs API usage: `Useful for debugging problems in your API;` :arrow_right: `Useful for debugging problems in your App;`.
  
  Also check what's going on with the missing `Content-Length` in the ASGI variant, it looks like the proposed middleware doesn't handle it particularly well.