curl --request POST \
  --url https://olive-gateway-a6ba.onrender.com/api/v1/webhooks/vult/cashin \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --header 'X-Webhook-Signature: <x-webhook-signature>' \
  --data '
{
  "amount": 123,
  "card_serial": "<string>"
}
'

{
  "message": "<string>",
  "new_balance": 123,
  "success": true,
  "transaction_id": "<string>"
}