title: Custom unique_together key name
body: <p>I have a model with a <a href="https://docs.djangoproject.com/en/dev/ref/models/options/#unique-together" rel="noreferrer"><code>unique_together</code></a> defined for 3 fields to be unique together:</p>
  
  <pre><code>class MyModel(models.Model):
      clid = models.AutoField(primary_key=True, db_column='CLID')
      csid = models.IntegerField(db_column='CSID')
      cid = models.IntegerField(db_column='CID')
      uuid = models.CharField(max_length=96, db_column='UUID', blank=True)
  
      class Meta(models.Meta):
          unique_together = [
              ["csid", "cid", "uuid"],
          ]
  </code></pre>
  
  <p>Now, if I attempt to save a <code>MyModel</code> instance with an existing csid+cid+uuid combination, I would get:</p>
  
  <pre><code>IntegrityError: (1062, "Duplicate entry '1-1-1' for key 'CSID'")
  </code></pre>
  
  <p>Which is correct. But, is there a way to customize that key name? (<code>CSID</code> in this case)</p>
  
  <p>In other words, can I provide a name for a constraint listed in <code>unique_together</code>?</p>
  
  <p><sup>As far as I understand, this is not covered in the documentation.</sup></p>