Transaction Identifiers do not match in Sandbox for iOS

• I have updated Purchases SDK to the latest version
• I have read the Contribution Guidelines
• I have searched the Community
• I have read docs.revenuecat.com
• I have searched for existing Github issues

Describe the bug
For iOS Sandbox transactions, the "transaction_id" field in the webhook is something like "StoreKitTest_Transaction_7d5df4466d669078a079d2c0d58f65d9_3" while in-app the result of purchaseProduct will have transactionIdentifier equal to just "3". I'm expecting these two things to match up for some fulfillment logic.

1. Environment
   1. Platform: iOS
   2. SDK version: 8.2.1
   3. OS version: iOS 18.0 (also tried in 16.4)
   4. Xcode/Android Studio version:
   5. React Native version: 0.73.6
   6. SDK installation (CocoaPods + version or manual):
   7. How widespread is the issue. Percentage of devices affected.
2. Debug logs that reproduce the issue
3. Steps to reproduce, with a description of expected vs. actual behavior
   1. Call purchaseProduct for a consumable product in iOS simulator
   2. Examine result.transaction.transactionIdentifier
      1. Expected: this value is unique and matches the txn id in the webhook request
      2. Actual: this value is not unique and does not match the txn id in the webhook request
4. Other information (e.g. stacktraces, related issues, suggestions how to fix, links for us to have context, eg. stackoverflow, etc.)

Additional context
N/A

No file or test is named. Start by reproducing the iOS simulator flow with purchaseProduct for a consumable, then compare transaction.transactionIdentifier with the webhook transaction_id. Done means the identifier behavior is consistent and unique across both results, or the supported limitation is clearly documented.