빌링키 발급 시 카드번호

 headers: {
  Authorization: 'Basic ' + Buffer.from(secretKey + ':').toString('base64'),
 'Content-Type': 'application/json',
},
json: {
  customerKey: userUUID,
  cardNumber: cardNumber,
  cardType: cardType,
  ownerType: ownerType,
  cardExpirationYear: cardExpirationYear,
  cardExpirationMonth: cardExpirationMonth,
  customerIdentityNumber: customerIdentityNumber,
  customerEmail: customerEmail
},
responseType: 'json',