curl --request POST \
  --url https://api.xentfi.com/v1/master-wallets/{masterId}/signing/transaction \
  --header 'Content-Type: application/json' \
  --header 'apiKey: <api-key>' \
  --header 'orgId: <api-key>' \
  --data '
{
  "blockchainId": "<string>",
  "signablePayload": {
    "data": "<string>",
    "to": "<string>",
    "value": "<string>"
  }
}
'

{
  "data": {
    "signature": "<string>",
    "signedTransaction": "<string>",
    "txHash": "<string>"
  }
}