title: Django How to pre-populate a form field with a argument form context
body: <p>I have the following view below. I would like to use '<code>email</code>' from the <code>get_context_data method</code> to pre-populate a form field in my UserAuthenticationForm form, how is this possible?</p>
  
  <p>View:</p>
  
  <pre><code>class CampaignLoginView(LoginView):
      model = Campaign
      form_class = UserAuthenticationForm
  
  
      def get_context_data(self, *args, **kwargs):
          context = super(CampaignLoginView, self).get_context_data(*args, **kwargs)
          user = AppUser.objects.get(pk=1)
          context['email'] = user.email  
  </code></pre>
  
  <p>Form:</p>
  
  <pre><code>class UserAuthenticationForm(AuthenticationForm):
  
      def __init__(self, *args, **kwargs):
          super(UserAuthenticationForm, self).__init__(*args, **kwargs)
  </code></pre>
  
  <p>Or is there is a way 'I should be doing it'?</p>