Spotify background playback problem on iOS
This is not a development issue, but well worth mentioning to all of you who have problem playing audio when the Spotify app for iOS enters the background.
It turns out that (for me) this happens when there are to many (many!) active programs. If so, Spotify is not added to the background process an can thus not continue to play.
Solve this by killing a few apps, then restart Spotify. Background playback should now work again.