title: django display message after POST form submit
body: <p>I have a page with a POST form, that have a action set to some url.<br>
  i.e assume this page url is <code>/form_url/</code> :
      
      ..
      </p>
  
  <p>The view in <code>/submit_url/</code> take care of the form data. After this, I want to return the same page of the form with a success message.
  In the view that take care for the POST form, I use <code>HttpResponseRedirect</code>, in order to "clear" the form data from the browser.
  But in this way I can't display a message in the form page, unless I do something like:</p>
  
  <pre><code>return HttpResponseRedirect("/form_url/?success=1")
  </code></pre>
  
  <p>and then check for this parameter in the template. I don't like this way, since if the user refreshes the page, he will still see the success message.</p>
  
  <p>I've noticed that in django admin site, the delete/add of objects does use redirect after POST submit, and still display a success message somehow. 
  How?</p>
  
  <p>I've already briefly seen django "messaging" app, but I want to know how it work first..</p>