title: Django: Model UniqueConstraint gives an error when migrating
body: <p>In my Django project the in one of the model I need to use two UniqueConstraint instances. But when I add that and do the migration after running makemigrations it gives an error in the terminal.</p>
  
  <p>Model class:</p>
  
  <pre><code>class MyDays(models.Model):
      class Meta:
          verbose_name = "My Day"
          verbose_name_plural = "My Days"
          constraints = [
              models.UniqueConstraint(fields=['userid', 'date', 'from'], condition=Q(status=1), name='user_date_from_a'),
              models.UniqueConstraint(fields=['userid', 'date', 'to'], condition=Q(status=1), name='user_date_to_b')
          ]
  
      id = models.BigAutoField(primary_key=True)
      userid = models.ForeignKey(User, on_delete=models.CASCADE, verbose_name="User")
      date = models.DateField(auto_now_add=False, editable=True, validators=[validate_date])
      from = models.TimeField(auto_now_add=False, editable=True)
      to = models.TimeField(auto_now_add=False, editable=True)
      status = models.ForeignKey(Status, on_delete=models.CASCADE, verbose_name="Status", default=1)
  </code></pre>
  
  <p>When I run python3 manage.py migrate, it gives the following error:</p>
  
  <blockquote>
    <p>django.core.exceptions.FieldError: Joined field references are not
    permitted in this query</p>
  </blockquote>
  
  <p>I need to have unique records only if the status is 1 along with the other 3 field combination. What am I doing wrong? How can I fix this error?</p>