POST /albums/youtube/{albumId} creates the album in your library and links
every song in it, provisioning each one as an external track without queueing
any download. The external id is kept on the album so saving it twice returns
a conflict instead of a duplicate, and albums can now hold external tracks,
not just the ones you uploaded.
Create, update, delete and list albums, plus adding and removing their tracks,
mirroring the playlist handlers. Only tracks the user uploaded can go into an
album, and removing one renumbers the rest so the tracklist stays 1..n.
Admin