What is the in_app_purchase package, and how does it provide a genuinely unified Flutter interface for handling actual real purchases through both the Google Play Store and the Apple App Store?

The in_app_purchase package provides a genuinely consistent, unified Dart interface specifically for implementing in app purchases, letting your app query the actual available products, initiate an actual real purchase, and properly verify that purchase's own genuine completion, all while internally and transparently delegating to each specific platform's own particular native billing system underneath, meaning you can write essentially just one single shared piece of purchase handling logic that genuinely properly works correctly across both Android and iOS, rather than needing to separately implement two entirely distinct platform specific purchase flows completely yourself.

final bool available = await InAppPurchase.instance.isAvailable();
final response = await InAppPurchase.instance.queryProductDetails({'premium_upgrade'});