Add support for starting a Live Activity with input-push-token on iOS 18

[ifrins]

Adds support for passing the input-push-token attribute, which is required in iOS 18 to start a Live Activity that wakes the app to get a push token to update the created Live Activity (which was not needed on iOS 17).

This has been tested with iOS 18.0 beta 6.

Apple docs: https://developer.apple.com/documentation/activitykit/starting-and-updating-live-activities-with-activitykit-push-notifications

[jchambers]

Hello, and thank you for the contribution! It's unclear to me why Apple has decided to model this as an integer; it seems like it's a boolean flag, right?

I think it probably makes sense to change the internal representation from a nullable Integer to just a boolean, then turn that into a 1 when we actually build the payload. Does that seem reasonable to you?

[jchambers]

A couple comments here:

1. If this is a single paragraph, I don't think we need <p> tags.
2. While this isn't incorrect, I do think there's more of the story we can and should tell for callers. In particular: this is for establishing a new channel for live activities, and it's intended for iOS 18 and newer. If it's helpful to you, I'd be happy to suggest specific wording!

[ifrins]

Sorry for the delay! I have updated the Javadoc to provide a bit more info. If the changes are fine, otherwise I'm open for any suggestions. In general, I don't like rehashing info from the source (Apple docs in this case), since from the outside most of the time it feels like trying to documenting undocumented behavior.