getExtensionFromRequest example

    public function __construct(
        private readonly FileUrlValidatorInterface $fileUrlValidator,
        private readonly bool $enableUrlUploadFeature = true,
        private readonly bool $enableUrlValidation = true,
        private readonly int $maxFileSize = 0
    ) {
    }

    public function fetchRequestData(Request $request, string $fileName): MediaFile
    {
        $extension = $this->getExtensionFromRequest($request);
        $expectedLength = (int) $request->headers->get('content-length');

        $inputStream = $request->getContent(true);
        $destStream = $this->openDestinationStream($fileName);

        try {
            $bytesWritten = $this->copyStreams($inputStream, $destStream, 0);
        } finally {
            fclose($inputStream);
            fclose($destStream);
        }