title: Updating dropdown list on the fly
body: <p><strong>Django 1.11</strong></p>
  
  <p>This is a private photo archive wich holds about About 10-20 users. 
  There are two models: Photo and Person.
  I want to describe which person is where in the picture.</p>
  
  <p>models.py</p>
  
  <pre><code>class Photo(models.Model):
      person = models.ForeignKey(Person,
                                 on_delete=models.PROTECT,
                                 blank=False,
                                 verbose_name=_("person"))
  </code></pre>
  
  <p>In forms.py I use ordinary ModelForm.</p>
  
  <p>Suppose, at the PhotoDetail page a user wants append a non-existent person. S/he clicks the dropdown list of persons. There is no appropriate person there. The user presses control and clicks on People in navigation bar. List of people appears in the new tab. S/he presses a plus sign. Inputs the user.</p>
  
  <p>The main problem: the newly created user is not accessible from that PhotoDetail page. If the user reloads it, then the full list is in front of them. But not now.</p>
  
  <p>Maybe I have to use AJAX here triggered by click on that dropdown list with people. </p>
  
  <p>Could you give me a piece of advice: what is the most practical way of solving this problem?</p>