consumable server side validation.

### Platform

- [X] iOS
- [ ] macOS
- [ ] tvOS

### In app purchase type

- [X] Consumable
- [ ] Non-consumable
- [ ] Auto-Renewable Subscription
- [ ] Non-Renewing Subscription

### Environment

- [X] Sandbox
- [ ] Production

### Version
Pod version 0.13.2

### Issue summary
Hello, mine is not a bug more like a question.
For our app we have subscription and consumable products for purchase. For subscription and consumable we want to implement server side validation (we use client side validation too using verifyReceipt)
What we do on subscription is after validation I sent base64 encrypted string (ex : MIISdAYJKoZIhvcNAQcCoIISZTCCEmECAQExCz....) to our server and our server validated it.

But for consumable product I can't get base64 encrypted receipt on validation object (for subscriptions I use receipt["latest_receipt"], the receipt object here is returned form verifyReceipt method).

So I want to know if there is any way to sent a base 64 encrypted string to our server to validate it using apple verification

Thanks