Use APNS to push now playing notifications to iOS clients

[jakebromberg]

Apple Push Notification Service is what allows servers to push notifications to iOS (and other Apple platform) clients. Pushing silent background notifications could be a delivery mechanism to keep clients always up to date for the currently playing item.

As it is, a client will ping the server at regular intervals (30s) to check for changes. This introduces delays between the time a track has changed and an update on the client side. Additionally, this has a noticeable delay on app launch, which can take several seconds. Honing in on the definition of "app launch" a little more, we can also use the term to describe the home screen widget, which goes through a loading state before displaying the current playcut. Using APNS would eliminate perceived loading times for an instantaneous experience.