ReadonlyactionOptional ReadonlyexternalValue to set. If empty, any existing value is removed.
Optional Readonlyshippingkey of the ShippingMethod to update.
This is required and valid only for Orders with Multiple ShippingMode.
An InvalidOperation error is returned if shippingKey is provided for Orders with Single ShippingMode, or omitted for Orders with Multiple ShippingMode.
A Shipping Method Tax Rate can be set if the Cart has the
ExternalTaxMode.