title: Get minimum value field name using aggregation in django
body: <p>I have a model with some fields like below</p>
  
  <pre><code>class Choclate(models.Model):
      name = models.CharField(max_length=256)
      price = models.IntegerField()
  </code></pre>
  
  <p>So i want to get the field name that has the <code>lowest price</code>  value, 
  so in order to get the <code>lowest price</code> value, we can do like below using <code>Aggregations</code></p>
  
  <pre><code>from django.db.models import Avg, Max, Min
  
  choclates = Choclate.objects.all()
  lowest_price = choclates.aggregate(Min('price'))
  </code></pre>
  
  <p>So finally how to get the <code>field name</code>, that related to lowest price value in django ?</p>