curl --request GET \
  --url https://test.deribit.com/api/v2/private/create_subaccount \
  --header 'Content-Type: application/json' \
  --data '
{
  "jsonrpc": "2.0",
  "id": 5414,
  "method": "private/create_subaccount",
  "params": {}
}
'

{
  "jsonrpc": "2.0",
  "id": 5414,
  "result": {
    "email": "[email protected]",
    "id": 13,
    "is_password": false,
    "login_enabled": false,
    "portfolio": {
      "eth": {
        "available_funds": 0,
        "available_withdrawal_funds": 0,
        "balance": 0,
        "currency": "eth",
        "equity": 0,
        "initial_margin": 0,
        "maintenance_margin": 0,
        "margin_balance": 0
      },
      "btc": {
        "available_funds": 0,
        "available_withdrawal_funds": 0,
        "balance": 0,
        "currency": "btc",
        "equity": 0,
        "initial_margin": 0,
        "maintenance_margin": 0,
        "margin_balance": 0
      }
    },
    "receive_notifications": false,
    "system_name": "user_1_4",
    "security_keys_enabled": false,
    "type": "subaccount",
    "username": "user_1_4"
  }
}