encode method

Implementation

Object encode() {
  return <Object?>[
    purchaseId,
    invoiceId,
    orderId,
    purchaseType,
    status,
    description,
    purchaseTime,
    price,
    amountLabel,
    currency,
    developerPayload,
    sandbox,
    productId,
    expirationDate,
    gracePeriodEnabled,
  ];
}