Create payment method

curl --request POST \
  --url https://api.{id}.gr4vy.app/payment-methods \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
  "expiration_date": "12/30",
  "number": "4111111111111111",
  "method": "card"
}'

{
  "type": "payment-method",
  "approval_url": "https://gr4vy.app/redirect/12345",
  "country": "US",
  "currency": "USD",
  "details": {
    "bin": "<string>",
    "card_type": "credit",
    "card_issuer_name": "<string>"
  },
  "expiration_date": "12/30",
  "fingerprint": "a50b85c200ee0795d6fd33a5c66f37a4564f554355c5b46a756aac485dd168a4",
  "label": "1234",
  "last_replaced_at": "2013-07-16T19:23:00.000+00:00",
  "method": "card",
  "mode": "card",
  "scheme": "visa",
  "id": "ef9496d8-53a5-4aad-8ca2-00eb68334389",
  "merchant_account_id": "default",
  "additional_schemes": [
    "eftpos-australia"
  ],
  "cit_last_used_at": "2013-07-16T19:23:00.000+00:00",
  "cit_usage_count": 50,
  "has_replacement": false,
  "last_used_at": "2013-07-16T19:23:00.000+00:00",
  "usage_count": 100,
  "buyer": {
    "type": "buyer",
    "id": "fe26475d-ec3e-4884-9553-f7356683f7f9",
    "merchant_account_id": "default",
    "display_name": "John Doe",
    "external_identifier": "buyer-12345",
    "billing_details": {
      "first_name": "John",
      "last_name": "Doe",
      "email_address": "john@example.com",
      "phone_number": "+1234567890",
      "address": {
        "city": "San Jose",
        "country": "US",
        "postal_code": "94560",
        "state": "California",
        "state_code": "US-CA",
        "house_number_or_name": "10",
        "line1": "Stafford Appartments",
        "line2": "29th Street",
        "organization": "Gr4vy"
      },
      "tax_id": {
        "value": "12345678931",
        "kind": "us.ein"
      }
    },
    "account_number": "<string>",
    "created_at": "2013-07-16T19:23:00.000+00:00",
    "updated_at": "2013-07-16T19:23:00.000+00:00"
  },
  "external_identifier": "card-12345",
  "status": "succeeded",
  "created_at": "2013-07-16T19:23:00.000+00:00",
  "updated_at": "2013-07-16T19:23:00.000+00:00"
}