title: How to access form data in `FormView.get_success_url()`
body: <p>Currently, I have a form that looks like this:</p>
  
  <pre><code>class SelectBoard(generic.FormView):
      form_class = forms.SelectBoard
  
      def form_valid(self, form):
          board_name = form.cleaned_data['name']
          return redirect('leaderboard', board_name=board_name)
  </code></pre>
  
  <p>However, it would be my preference to do the more idiomatic thing, and use <code>get_success_url</code>. Something like this:</p>
  
  <pre><code>class SelectBoard(generic.FormView):
      form_class = forms.SelectBoard
  
      def get_success_url(self):
          form = ???
          board_name = form.cleaned_data['name']
          return reverse('leaderboard', board_name=board_name)
  </code></pre>
  
  <p>However, the form is not passed to <code>get_success_url</code>, and unlike many other pieces of request context (like <code>self.request</code>, <code>self.kwargs</code>, or <code>self.object</code> (in <code>DetailView</code>)), the form is not attached as an attribute at any point in the standard <code>FormView</code> dispatch sequence. Is there any good way to access cleaned &amp; validated form data in <code>get_success_url</code> (that is, without having to access <code>self.request.POST</code> or reconstruct the form from scratch)?</p>