Describe the bug

When using a scene delegate or multiple windows (not entirely sure about the internals) in iOS, PaymentSheet fails to load.

Related tickets/bugs:

• presentPaymentSheet() not working in scene-based life-cycle apps stripe/stripe-react-native#2201
  • (Fixed in Fix how we get root VC for scene based apps stripe/stripe-react-native#2216)
• Not open PaymentSheet #2158

Tentative Fix

I'd open a PR, but not confident on my swift/iOS skills.

https://stackoverflow.com/questions/57134259/how-to-resolve-keywindow-was-deprecated-in-ios-13-0

Replaced

paymentSheetViewController = UIApplication.shared.delegate?.window??.rootViewController ?? UIViewController()

With

let keyWindow = UIApplication.shared.connectedScenes
   .filter({$0.activationState == .foregroundActive})
   .compactMap({$0 as? UIWindowScene})
   .first?.windows
   .filter({$0.isKeyWindow}).first
 paymentSheetViewController = keyWindow?.rootViewController ?? UIViewController()

There are a few instances of the UIApplication.shared.delegate?.window? in the packages/stripe_ios directory, I cloned the repo, set up a pubspec_override.yaml and replaced all of those, with good results (at least in the emulator).

To Reproduce
Steps to reproduce the behavior:

1. Have a working project with flutter_stripe
2. Add and configure a multi-scene depency (e.g., car_play)
3. PaymentSheet stops working.

Expected behavior

PaymentSheet should continue to work.

Smartphone / tablet

• Device: iPhone (15, 16)
• OS: iOS 13+
• Package version: 12.0.2, 12.10
• Flutter version: Flutter 3.35.3

Additional context

I suspect other flutter_stripe features to fail with similar setups but can't confirm.