public function extractMeta(string $requestedKey) : string
    {
        $uploadMetaData = $this->request->headers->get('Upload-Metadata');

        if (empty($uploadMetaData)) {
            return '';
        }

        $uploadMetaDataChunks = explode(',', $uploadMetaData);

        foreach ($uploadMetaDataChunks as $chunk) {
            list($key, $value) = explode(' ', $chunk);

            if ($key === $requestedKey) {
                return base64_decode($value);
            }
        }

        return '';
    }