User balances channel

// subscribe request
{
    "command": "subscribe",
    "identifier": "{\"channel\":\"AccountChannel\"}"
}

// confirmation
{
    "type": "confirm_subscription",
    "identifier": "{\"channel\":\"AccountChannel\"}"
}

// response structure
{
    "identifier": "{\"channel\":\"AccountChannel\"}",
    "message": {
        "balances": [
            {
                "balance": "1.24705",
                "available_balance": "1.24705",
                "hold_balance": "0.0",
                "currency_code": "btc",
                "currency_name": "Bitcoin"
            },
            {
                "balance": "11.99342",
                "available_balance": "11.99342",
                "hold_balance": "0.0",
                "currency_code": "eth",
                "currency_name": "Ethereum"
            }
        ]
    }
}