[in_app_purchase_storekit] Replace deprecated offer code API

[LouiseHsu]

Fixes flutter/flutter#162914

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[flutter-dashboard]

This pull request is not mergeable in its current state, likely because of a merge conflict. Pre-submit CI jobs were not triggered. Pushing a new commit to this branch that resolves the issue will result in pre-submit jobs being scheduled.

[LouiseHsu]

@gemini-code-assist hewwo

[gemini-code-assist]

Code Review

This pull request adds support for offer codes in StoreKit 2 for the in_app_purchase_storekit package. Key changes include the implementation of presentOfferCodeRedeemSheet in the Swift backend, updates to the Dart platform addition to support StoreKit 2, and the addition of a redemption button in the example application. The iOS example was also updated to utilize scene delegates and implicit engine delegation. Review feedback highlights a potential issue where the Dart Future could hang if OS version requirements are not met in the Swift code, the need for a minimum Flutter version constraint in the plugin's pubspec, and the presence of accidental changes to the example app's bundle identifier and Xcode project version.

[gemini-code-assist]

The completion handler is not called if the OS version requirements are not met (iOS < 16.0 or macOS < 15.0), or if the platform is neither iOS nor macOS. This will cause the Dart Future to hang indefinitely. An error should be returned in these cases to ensure the caller receives a response.

  func presentOfferCodeRedeemSheet(completion: @escaping (Result<Void, Error>) -> Void) {
    #if os(iOS)
      if #available(iOS 16.0, *) {
        guard let windowScene = self.registrar?.viewController?.view.window?.windowScene else {
          let error = PigeonError(
            code: "storekit2_missing_key_window_scene",
            message: "Failed to fetch key window scene",
            details: "registrar.viewController.view.window.windowScene returned nil."
          )
          completion(.failure(error))
          return
        }
        Task { @MainActor in
          do {
            try await AppStore.presentOfferCodeRedeemSheet(in: windowScene)
            completion(.success(()))
          } catch {
            completion(.failure(error))
          }
        }
      } else {
        completion(.failure(PigeonError(
          code: "storekit2_unsupported_version",
          message: "Offer code redemption via StoreKit 2 requires iOS 16.0 or later.",
          details: nil
        )))
      }
    #elseif os(macOS)
      if #available(macOS 15.0, *) {
        guard let viewController = self.registrar?.viewController else {
          let error = PigeonError(
            code: "storekit2_missing_view_controller",
            message: "Failed to fetch view controller",
            details: "registrar.viewController returned nil."
          )
          completion(.failure(error))
          return
        }

        Task { @MainActor in
          do {
            try await AppStore.presentOfferCodeRedeemSheet(from: viewController)
            completion(.success(()))
          } catch {
            completion(.failure(error))
          }
        }
      } else {
        completion(.failure(PigeonError(
          code: "storekit2_unsupported_version",
          message: "Offer code redemption via StoreKit 2 requires macOS 15.0 or later.",
          details: nil
        )))
      }
    #else
      completion(.failure(PigeonError(
        code: "storekit2_unsupported_platform",
        message: "Offer code redemption via StoreKit 2 is not supported on this platform.",
        details: nil
      )))
    #endif
  }

[LouiseHsu]

this is fine bc users should not be on storekit 2 below ios 15

[gemini-code-assist]

The plugin now utilizes new Flutter APIs such as registrar.addSceneDelegate and FlutterSceneLifeCycleDelegate. A minimum Flutter version constraint should be added to the environment section to prevent compilation failures for users on older Flutter SDKs.

environment:
  sdk: ^3.9.0
  flutter: ">=3.38.0"

[gemini-code-assist]

The bundle identifier has been changed to include a '9' at the end. This appears to be a local testing change and should be reverted to maintain the correct identifier for the example app.

				PRODUCT_BUNDLE_IDENTIFIER = dev.flutter.plugins.in_app_purchaseExample;

[gemini-code-assist]

The objectVersion has been downgraded from 60 to 54. This typically occurs when a project is opened in an older version of Xcode. It should be reverted to 60 to maintain consistency with the repository's development environment.

	objectVersion = 60;

[gemini-code-assist]

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