- Re-run notify if Tus returns error "upload is still in process".
- Poll status every 10 seconds (12 times) while response is 202.
- Use horizontal progress bar with determinate progress while Tus is
  uploading. This lets there be a meaningful indicator while uploading a
  large file.

The "Check Status" button (used when the retry count has been exceeded
polling status) is only shown in the Publish Form, since it won't
navigate away until the publish is successful.

Fix: #365