developerPayload property
The payload specified by the developer when the purchase was acknowledged or consumed.
The value is null if it wasn't specified when the purchase was acknowledged or consumed.
The developerPayload is removed from BillingClientWrapper.acknowledgePurchase, BillingClientWrapper.consumeAsync, InAppPurchaseConnection.completePurchase, InAppPurchaseConnection.consumePurchase
after plugin version 0.5.0. As a result, this will be null for new purchases that happen after updating to 0.5.0.
Implementation
final String? developerPayload;