Order updated with the versioning conversion

Order.ts

class Order {
  protected whenOrderCreated(event: OrderCreated): void {
        this._items = event.items;
        this._status = OrderStatus.OPEN;
        this._amount = event.amount;
        this._destination = event.destination;
        this._customerId = event.customerId;

        // New code - detect if we have the property first
        if (event.hasOwnProperty('deliveryMethod') {
          this._deliveryMethod = event.deliveryMethod;
        } else {
          // Assume one default from business
          this._deliveryMethod = 'Standard';
        }
    }
}