title: Proper way to handle custom submit button at django custom model admin add page
body: <p>I want to add an extra button at <code>submit_line.html</code> that does exactly the same thing as submit but it sets certain field to something else while sending post request to server.</p>
  
  <p>Say I have a blog as model, I want to add "save as draft" as button.</p>
  
  <p>My <code>submit_line.html</code> looks like this:</p>
  
  <pre><code>{% load i18n admin_urls %}
  &lt;div class="submit-row"&gt;
  {% if show_save %}&lt;input type="submit" value="{% trans 'Save' %}" class="default" name="_save" /&gt;{% endif %}
  
  {% if show_save_as_draft %}&lt;input type="submit" value="save_as_draft" class="default" name="_save" /&gt;{% endif %}
  
  
  {% if show_delete_link %}
      {% url opts|admin_urlname:'delete' original.pk|admin_urlquote as delete_url %}
      &lt;p class="deletelink-box"&gt;&lt;a href="{% add_preserved_filters delete_url %}" class="deletelink"&gt;{% trans "Delete" %}&lt;/a&gt;&lt;/p&gt;
  {% endif %}
  {% if show_save_as_new %}&lt;input type="submit" value="{% trans 'Save as new' %}" name="_saveasnew" /&gt;{% endif %}
  {% if show_save_and_add_another %}&lt;input type="submit" value="{% trans 'Save and add another' %}" name="_addanother" /&gt;{% endif %}
  {% if show_save_and_continue %}&lt;input type="submit" value="{% trans 'Save and continue editing' %}" name="_continue" /&gt;{% endif %}
  &lt;/div&gt;
  </code></pre>
  
  <p>Now I don't understand how it is making this request, so I can't modify it, so please help me regarding this.</p>