`/verifyReceipt` endpoint is forbidden by Apple

### Platform
- [x] iOS
- [x] macOS
- [x] tvOS

### In-app purchase type
- [x] Consumable
- [x] Non-consumable
- [x] Auto-Renewable Subscription
- [x] Non-Renewing Subscription

### Environment
- [x] Sandbox
- [x] Production

### Version
Latest (0.15.0), maybe all versions

### Related issues
- #101, but it is written as a suggestion to implement while it is actually obligatory!

## Report

### Issue summary
> "Important: Do not call the App Store server /verifyReceipt endpoint from your app."
> - [Apple Developer Documentation](https://developer.apple.com/library/archive/releasenotes/General/ValidateAppStoreReceipt/Chapters/ValidateRemotely.html#//apple_ref/doc/uid/TP40010573-CH104-SW1)

### What did you expect to happen
`verifyReceipt` endpoint is **not used** (how it is explained in the official Apple documentation)

### What happened instead
`verifyReceipt` endpoint is used