curl -X POST 'https://developers.flouci.com/api/v2/cancel_payment' \
  -H 'Content-Type: application/json' \
  -H 'Authorization: Bearer <PUBLIC_KEY>:<PRIVATE_KEY>' \
  -d '{ \
    "payment_id": "a1b2c3d4-e5f6-7890-1234-567890abcdef" \
  }'

{
  "result": {
    "success": true
  }
}