getThumbnailFileExtensionFromUrl example

    $remote_thumbnail_url = $remote_thumbnail_url->toString();
    $hash = Crypt::hashBase64($remote_thumbnail_url);
    $files = $this->fileSystem->scanDirectory($directory, "/^$hash\..*/");
    if (count($files) > 0) {
      return reset($files)->uri;
    }

    // The local thumbnail doesn't exist yet, so we need to download it.     try {
      $response = $this->httpClient->request('GET', $remote_thumbnail_url);
      if ($response->getStatusCode() === 200) {
        $local_thumbnail_uri = $directory . DIRECTORY_SEPARATOR . $hash . '.' . $this->getThumbnailFileExtensionFromUrl($remote_thumbnail_url, $response);
        $this->fileSystem->saveData((string) $response->getBody(), $local_thumbnail_uri, FileSystemInterface::EXISTS_REPLACE);
        return $local_thumbnail_uri;
      }
    }
    catch (TransferException $e) {
      $this->logger->warning('Failed to download remote thumbnail file due to "%error".', [
        '%error' => $e->getMessage(),
      ]);
    }
    catch (FileException $e) {
      $this->logger->warning('Could not download remote thumbnail from {url}.', [