title: Django How to organize models so there is only one owner
body: <p>I have two models Company and User:</p>
  <pre class="lang-py prettyprint-override"><code>class Company(models.Model):
      name = CharField(&quot;Name&quot;, max_length=60)
      owner = OneToOneField(
          &quot;Employee&quot;, related_name='owner', on_delete=SET_NULL, null=True)
  
  class BaseUser(AbstractBaseUser, PermissionsMixin):
  
      objects = CustomUserManager()
  
      join_date = DateTimeField(default=timezone.now)
      name = CharField(&quot;Name&quot;, max_length=60)
      email = EmailField(('Email'), unique=True)
      company = ForeignKey(Company, on_delete=models.CASCADE)
  </code></pre>
  <p>I need to have only one User as owner. I made it so two models point to each other which doesn't seem right. Is there a way to fix it and still have only one possible owner? I know standard way  would be to add <code>is_owner = Boolean</code> to User but it allows other Users to be owners.</p>