title: Django models use id group as ForeignKey
body: <p>I am developing one site and need to link table records to group id so I wrote my model for db but when I try to insert foreignkey i receive  errors on makemigrations:</p>
  <p>(fields.E300) Field defines a relation with model 'Group', which is either not installed, or is abstract.<br />
  and
  sito_boe.Boe.group_id: (fields.E307) The field sito_boe.Boe.group_id was declared with a lazy reference to 'sito_boe.group', but app 'sito_boe' doesn't provide model 'group'
  Here is my model.
  I just searched on web and documentation without luck, Anyone can help me?
  Here is my code:</p>
  <pre><code>from django.contrib.auth.models import Group
  
  #Group.auth_group
  class Boe(models.Model):
      &quot;&quot;&quot;Model representing an author.&quot;&quot;&quot;
      Name = models.CharField(max_length=100,verbose_name=&quot;Nome&quot;)
      Geo_POS = models.CharField(max_length=100,verbose_name=&quot;Coordinate&quot;)
      Luogo = models.TextField(verbose_name=&quot;Posizione&quot;)
      created_date = models.DateTimeField(default=timezone.now)
      #group_id = models.CharField(max_length=100,verbose_name=&quot;Gruppo&quot;)
      id_boa = models.CharField(max_length=20,unique=True,blank=False,verbose_name=&quot;Identificativo boa&quot;,help_text='Enter field boaXX')
      group_id = models.ForeignKey('Group.auth_group', on_delete=models.SET_NULL, null=True)
      
      def __str__(self):
          &quot;&quot;&quot;String for representing the Model object.&quot;&quot;&quot;
          return self.Name
  
      class Meta:
          ordering = ['Name']
          verbose_name_plural = &quot;Boe&quot;
      
      def get_absolute_url(self):
          &quot;&quot;&quot;Returns the url to access a particular author instance.&quot;&quot;&quot;
          return reverse('listaboe', args=[str(self.id)])
  </code></pre>