SKPaymentTransactionObserver.swift

extension InAppManager: SKPaymentTransactionObserver {
    func paymentQueue(_ queue: SKPaymentQueue, updatedTransactions transactions: [SKPaymentTransaction]) {
        for transaction in transactions {
            guard let productType = ProductType(rawValue: transaction.payment.productIdentifier) else {fatalError()}
            switch transaction.transactionState {
            case .purchasing:
            case .purchased:
            case .failed:
            case .restored:
            case .deferred:
            }
        }
    }
}