title: Django : get the last item of manytomanyfield
body: <p>With these models :</p>
  
  <pre><code>class Message(models.Model):
      text = models.CharField(max_length=200)
      date_send = models.DateTimeField(auto_now_add=True,editable=False)
      emeteur = models.ForeignKey(User,null=True,related_name="+")
  
      class Meta :
          abstract = True
  
  
  class MessagePerso(Message) :
      read_at = models.DateTimeField(("read at"), null=True, blank=True)
  
  class Conversation(models.Model):
      title = models.CharField(max_length=90)
      creator = models.ForeignKey(User,null=True,related_name="CreatorConversation")
      recipient = models.ForeignKey(User,null=True,related_name="RecipientConversation")
      created_at = models.DateTimeField(auto_now_add=True,editable=False)
      messages = models.ManyToManyField(MessagePerso)
  </code></pre>
  
  <p><strong>So, for each Conversation I want the text of the last MessagePerso created (ManyToManyField in Conversation) and others informations.</strong></p>
  
  <p>So for now, I have this :</p>
  
  <pre><code>def .. :
      u = request.user
      conversations = Conversation.objects.filter(Q(creatorr=u)|Q(destinataire=u)).annotate(nbMsg=Count('messages'),date=Max('messages__date_send')).order_by('date','id')
  </code></pre>
  
  <p>I don't have the the text of last message created for each Conversation, how makes it ?</p>