title: Django ModelForm with Select Widget - Use object.uid as default option value instead of object.id
body: <p>I have a form inheriting from ModelForm as such:</p>
  
  <pre><code>class ChildModel(ModelForm):
        class Meta:
            model = Documents
            fields = ('secretdocs')
            widgets = {
                'secretdocs': Select(attrs={'class': 'select'}),
            }
  </code></pre>
  
  <p>The model "secretdocs" has a uid.  But when it prints out the select and option, the option values appear as such:</p>
  
  <pre><code>&lt;select class="select" id="id_secretdocs" name="secretdocs"&gt;
      &lt;option value="1"&gt;My Secret Doc&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>But I want it to instead have the uid of the option:</p>
  
  <pre><code>&lt;select class="select" id="id_secretdocs" name="secretdocs"&gt;
      &lt;option value="cd2feb4a-58cc-49e7-b46e-e2702c8558fd"&gt;My Secret Doc&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>I've so far tried to use BaseForm's data object and overwriting Select's value_from_datadict method but I'm pretty sure that wasn't the right approach.  Does anyone know how I can do this?</p>
  
  <p>Thanks in advance.</p>