V1

{
  "body": {
    "childSessionMode": "string (TEXT_TO_PAY)",
    "customer": {
      "email": "string",
      "phone": {
        "countryCode": "string",
        "number": "string"
      }
    },
    "lang": "string",
    "paymentMethodType": "string (CARD)" <REMOVED>
  },
  "headers": {
    "Accept": "application/json",
    "Authorization": "string (Bearer token, optional)",
    "Content-Type": "application/json",
    "X-Correlation-Id": "string (optional)",
    "X-Merchant-Id": "string (uuid)",
    "X-Request-Id": "string (optional)"
  },
  "method": "POST",
  "path": "/checkout-sessions/{checkout-session-id}/child-sessions" <MODIFIED>
}

V2

{
  "body": {
    "childSessionMode": "string (TEXT_TO_PAY)",
    "customer": {
      "email": "string",
      "phone": {
        "countryCode": "string",
        "number": "string"
      }
    },
    "lang": "string",
    "uiVersion": "string" <ADDED>
  },
  "headers": {
    "Accept": "application/json",
    "Authorization": "string (Bearer token, optional)",
    "Content-Type": "application/json",
    "X-Correlation-Id": "string (optional)",
    "X-Merchant-Id": "string (uuid)",
    "X-Request-Id": "string (optional)"
  },
  "method": "POST",
  "path": "/v2/checkout-sessions/{checkout-session-id}/child-sessions" <MODIFIED>
}