code: public function upload($key, UploadedFile $file, $overwrite = false)
      {
          try {
              $this->uploadToFlysystem($key, $file);
          } catch (FileExistsException $exception) {
              if (!$overwrite) {
                  throw new \RuntimeException(sprintf('The file with key "%s" is exists.', $key));
              }
              $this->filesystem->delete($key);
              $this->uploadToFlysystem($key, $file);
          }
          @unlink($file->getPathname()); //remove old
          return true;
      }
docs: {@inheritdoc}