As mentioned in LB-891, as we get more and more users listening to tracks on spotify, it takes longer to get back and process a user.

This means that now playing notifications will also take longer and longer to update, and as a result they won't be consistent with what the user is listening to.

In order to keep these notifications up-to-date, we should split the functionality of the spotify importer into two - one for the listen importer and one for the now playing reporter. This will have the effect of making the listen importer complete faster (improving some of the points mentioned in LB-891), and will also improve the update speed of now-playing notifications.

We should consider keeping track of which users are actually listening to something currently - if they're actively listening to something then we want their now playing to update more frequently (e.g. every 10-30 seconds if possible). If they're not listening to anything we could check less frequently (every 2-5 minutes?) and then if we get a notification, move them into the frequent check list. If we notice that a user stops listening (no more now playing notfications), move them back to the less-frequent list