고객 조회

curl --request GET \
  --url https://xapi.bolta.io/v1/customers/{customerKey} \
  --header 'Authorization: Basic <encoded-value>'

{
  "customerKey": "<string>",
  "identificationNumber": "<string>",
  "organizationName": "<string>",
  "representativeName": "<string>",
  "taxRegistrationId": "<string>",
  "certificate": {
    "issuedAt": "<string>",
    "expiresAt": "<string>"
  }
}