code: private function createUniqueFilename( $filename )
      {
          $full_size_dir = config('dropzoner.upload-path');
          $full_image_path = $full_size_dir . $filename . '.jpg';
  
          if (\File::exists($full_image_path)) {
              // Generate token for image
              $image_token = substr(sha1(mt_rand()), 0, 5);
              return $filename . '-' . $image_token;
          }
  
          return $filename;
      }
docs: Check upload directory and see it there a file with same filename
  If filename is same, add random 5 char string to the end
  
  @param $filename
  @return string