curl --request POST \
  --url https://demo-api.mobula.io/api/2/perp/payloads/create-account \
  --header 'Content-Type: application/json' \
  --data '
{
  "timestamp": 123,
  "signature": "<string>",
  "dex": "gains",
  "chainId": "<string>",
  "accountIndex": 123,
  "apiKeyIndex": 123
}
'

{
  "success": true,
  "data": {
    "action": "<string>",
    "dex": "<string>",
    "chainId": "<string>",
    "transport": "offchain-api",
    "payloadStr": "<string>",
    "marketId": "<string>"
  }
}