message: [fix] url shortner for long explore url
  redirect explore url with r parameter
  redirect to relative path
diff: @@ -761,8 +761,13 @@ class R(BaseSupersetView):
  @expose('/<url_id>')
  def index(self, url_id):
  url = db.session.query(models.Url).filter_by(id=url_id).first()
  - if url:
  - return redirect('/' + url.url)
  + if url and url.url:
  + explore_url = '//superset/explore/?'
  + if url.url.startswith(explore_url):
  + explore_url += f'r={url_id}'
  + return redirect(explore_url[1:])
  + else:
  + return redirect(url.url[1:])
  else:
  flash('URL to nowhere...', 'danger')
  return redirect('/')
  