The credit card that can be used to fund a payment.
valid_untilstringOptionallinksobject<link_description>[]OptionalhrefstringRequiredbilling_addressobject<address>OptionalstatestringOptionalcountry_codestring<country_code>RequiredNote: The country code for Great Britain isGBand notUKas used in the top-level domain names for that country. Use the `C2` country code for China worldwide for comparable uncontrolled price (CUP) method, bank card, and cross-border transactions.