✅ powershell post MultipartContent weird behavior

Add-Type -assemblyname System.Net.Http

function Create-Multipart-Settings($section_data) {
    $multipartContent = [System.Net.Http.MultipartFormDataContent]::new()

    $uploadStringHeader = [System.Net.Http.Headers.ContentDispositionHeaderValue]::new('form-data')
    $uploadStringHeader.Name = "set_params"

    $uploadStringContent = [System.Net.Http.StringContent]::new('upload');
    $uploadStringContent.Headers.ContentDisposition = $uploadStringHeader;

    $multipartContent.Add($uploadStringContent, 'set_params')

    $contentStringHeader = [System.Net.Http.Headers.ContentDispositionHeaderValue]::new('form-data')
    $contentStringHeader.Name = "user_file"

    $fileStringContent = [System.Net.Http.StringContent]::new($section_data);
    $fileStringContent.Headers.ContentDisposition = $contentStringHeader

    $multipartContent.Add($fileStringContent, 'user_file', 'set_params.dat')
    return $multipartContent
}

$mc = Create-Multipart-Settings 'data'
$headers = @{}
$headers.Add(...) # authorization stuff
$headers.Add('Content-Type', 'application/x-www-form-urlencoded')
Invoke-WebRequest -Body $mc -Method 'POST' -Uri 'http://...' -headers $headers -TimeoutSec 1800