Add cross-origin redirect delegate

[pfeiffer]

Follow-up of #201.

As discussed in #201 it would be preferrable to handle cross-origin redirects in the SessionDelegate.

This PR takes a stab at that to get the ball rolling so we can get feature parity between iOS and Android libs again :-)

[joemasilotti]

I like this approach much better! I tested running against the demo PR and everything works as expected after adding the require delegate callback.

I added one suggestion to make the documentation even more obvious where the cross-origin redirect handling code should go.

[joemasilotti]

Suggested change

	navigationController.popViewController(animated: false)
	UIApplication.shared.open(url)
	func session(_ session: Session, didProposeVisitToCrossOriginRedirect url: URL) {
	navigationController.popViewController(animated: false)
	UIApplication.shared.open(url)
	}

[tim-vandecasteele]

Hi @pfeiffer @joemasilotti , I was wondering if there is a reason this is not merged? Is this waiting for something, or just not merged yet because of time?

[joemasilotti]

We migrated to Hotwire Native before resolving this issue. Please open an issue/PR on that repo if you'd like to continue the discussion!

[jayohms]

I'm closing this since the approach does not work across all applications with the javascript Fetch API with varying CORS restrictions. A different approach was implemented on the Android side in Hotwire Native: hotwired/hotwire-native-android#82

We're going to bring this same approach to Hotwire Native iOS as well, shortly.