Via Tender: Redirect URL for session requests

Assigned to Tender discussion #668. As reported in Tender:

Hey!

I have a few questions about the API v3.

I just created an API wrapper class in PHP (the currently advised PHP Class does not support all API functionally, and it was a bit to spanish for me :) ), which I will publish soon on Github, and noticed the following points/questions.

1. Unused id part in Account Favorite Movies, Account Rated Movies, Movie Add Rating and Account Add Favorite.
   All four requests work exactly the same when entering a zero instead of the asked for ID (the account ID that belongs to the session ID).

2. Lack of Account Wishlist Movies and Account Add Wishlist
   It would be very useful, I think, to have the possibility to do this through the API.

3. Authorization callback.
   It might be my lack of understanding the Authorization process:

4. Request a token: http://api.themoviedb.org/3/authentication/token/new?api_key=mykey123

5. Point the user to the URL defined in the Authentication-Callback response header.
6. The user clicks allow.
7. Request a session ID with the token: http://api.themoviedb.org/3/authentication/session/new?api_key=myke...

But how does a developer know if the user has allowed, denied, or just closed the window? When does the developer know he can request a Session ID?
Shouldn't it be possible for the developer to specify a redirect url, so TMDb can send a user back to a place the developer specified?

Again, it might be my lack of understanding, if it is, I'm pretty stoked to hear the answer :)