fix: corrected transactionReason when a previously cancelled subscription was purchased again (#21)

Hello, I discovered that `transactionReason` was incorrectly set to
`RENEW` instead of `PURCHASE`, for iOS purchases that had been
previously cancelled and then purchased again in the
`purchaseUpdatedListener` callback.

This fix restores the previous logic for determining
`transactionReason`, consistent with the behavior in react-native-iap
versions 12.x.x and 13.x.x and real App Store data encoded in
`jsonRepresentation`.

hyochan/react-native-iap#3056

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Bug Fixes**
* Improved accuracy in detecting subscription renewals, ensuring renewal
events are correctly identified.
* Reduces instances where subscriptions might appear incorrectly as new
purchases or non-renewals.
* Leads to more reliable subscription status, history, and related
notifications for users.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: nahlebn1k

Sources/Helpers/StoreKitTypesBridge.swift

@@ -333,6 +333,10 @@ private extension StoreKitTypesBridge {
         let string: String
         let uppercased: String
     }
+    
+    struct JSONTransactionReason: Codable {
+        let transactionReason: String
+    }
 
     static func transactionReasonDetails(from transaction: StoreKit.Transaction) -> TransactionReason {
         if let revocation = transaction.revocationReason {
@@ -358,9 +362,8 @@ private extension StoreKitTypesBridge {
         }
 
         // Try to infer renewal for iOS <17
-        if transaction.productType == .autoRenewable,
-           let expirationDate = transaction.expirationDate,
-           expirationDate > transaction.purchaseDate {
+        if let decodedReason = try? JSONDecoder().decode(JSONTransactionReason.self, from: transaction.jsonRepresentation),
+            decodedReason.transactionReason == "RENEWAL" {
             return TransactionReason(lowercased: "renewal", string: "renewal", uppercased: "RENEWAL")
         }