title: Django subquery with aggregate
body: <p>I have two models called <code>User</code> and <code>Transaction</code> . Here i want to get the all the users with total sum of the transaction amount where status is success.</p>
  
  <p>I have tried with subquery but i am not getting how to annotate the aggregate of the subquery with conditions</p>
  
  <pre><code>class User(models.Model):
    name = models.CharField(max_length=128)
  
  class Transaction(models.Model):
    user = models.ForeignKey(User)
    status = models.CharField(choices=(("success", "Success"),("failed", "Failed")))
     amount = models.DecimalField(max_digits=10, decimal_places=2)
  
  subquery = Transaction.objects.filter(status="success", user=OuterRef('pk')).aggregate(total_spent = Coalesce(Sum('amount'), 0))
  
  query = User.objects.annotate(total_spent=Subquery(subquery:how to do here ?)).order_by(how to order here by total_spent)
  </code></pre>