title: Django model unique together both ways
body: <p>Many questions already on this topic, but not what i'm searching for.</p>
  
  <p>I have this <code>Model</code>:</p>
  
  <pre><code>class Options(TimeStampedModel)
      option_1 = models.CharField(max_length=64)
      option_2 = models.CharField(max_length=64)
  
      class Meta:
          unique_together = ('option_1', 'option_2')
  </code></pre>
  
  <p>Now I have a unique constraint on the fields.
  Is there a way to also define this the other way around so that it doesn't matter what was <code>option_1</code> and what was <code>option_2</code></p>
  
  <p>As example:</p>
  
  <pre><code>Options.create('spam', 'eggs') # Allowed
  Options.create('spam', 'eggs') # Not allowed
  Options.create('eggs', 'spam') # Is allowed but should not be
  </code></pre>
  
  <p>Thanks in advance!</p>