Return the payment method for a specified shopping cart.
/V1/guest-carts/{cartId}/selected-payment-method
(Required) The cart ID.
<string>
Add a specified payment method to a specified shopping cart.
/V1/guest-carts/{cartId}/selected-payment-method
(Required) The cart ID.
<string>
application/json
{"method":{"method":"<string>","po_number":"<string>","additional_data":["<string>","<string>"],"extension_attributes":{"agreement_ids":["<string>","<string>"]}}}