IMPROVEMENTS:
- Nullable properties now are NOT converted to empty int/bool/float/string in AppMetadata, RenewalInfo, ResponseBodyV2, TransactionInfo, kudos to @dbrkv for pointing this out
- ArrayTypeCastGenerator moved to the separate class
- PHPUnit tests introduced (just the first one for ArrayTypeCastGenerator atm)
- Examples reworked a bit (RenewalInfo/TransactionInfo printing moved to the separate helper function)