Azure Function Powershell Return File

$stockData = Import-Csv -Path $extractPath\STOCK.csv

$outputObject = $stockData | Select-Object "Stock Code",@{Name="RRP Ex";Expression={$_.RRP / 1.1}}

$csv=$outputObject | Convertto-Csv -NoTypeInformation

$response = ConvertTo-JSON @{
    Body= "$csv";
    Headers=@{
        'Content-Disposition'='attachment;filename="file.csv"';
        'Content-Type'='application/octet-stream';
    };
}
Out-File -Encoding utf8 -FilePath $res -inputObject $response