title: i have problem with one to one extends user model
body: <p>hi friends i want extends user model with fields from other table (structure) as foreignkey .. i will show you my models and the error after creation of super user </p>
  
  <pre class="lang-py prettyprint-override"><code>from django.db import models
  from django.contrib.auth.models import User
  from immob.models import structure
  from django.db.models.signals import post_save
  from django.dispatch import receiver
  
  
  class Profile(models.Model):
      User = models.OneToOneField(User, on_delete=models.CASCADE)
      structure_id = models.ForeignKey(structure, on_delete=models.CASCADE, default=0)
  
  
      @receiver(post_save, sender=User)
      def create_user_utilisateur(sender, instance, created, **kwargs):
          if created:
          Profile.objects.create(User=instance)
  
  
      @receiver(post_save, sender=User)
      def save_user_utilisateur(sender, instance, **kwargs):
          instance.profile.save()
  </code></pre>
  
  <p>Error message:</p>
  
  <pre><code>[p-amc-dgps-er@192-168-150-254 Invest_App]$ python3 manage.py createsuperuser
  Username (leave blank to use 'p-amc-dgps-er'): admin
  Email address: admin@admin.dz
  Password: 
  Password (again): 
  Error: Your passwords didn't match.
  Password: 
  Password (again): 
  Traceback (most recent call last):
    File "/usr/lib/python3.6/site-packages/django/db/backends/base/base.py", line 239, in _commit
      return self.connection.commit()
  psycopg2.errors.ForeignKeyViolation: ERREUR:  une instruction insert ou update sur la table �� compte_profile �� viole la contrainte de cl��
  ��trang��re �� compte_utilisateur_structure_id_id_df7f99e8_fk_immob_str ��
  DETAIL:  La cl�� (structure_id_id)=(0) n'est pas pr��sente dans la table �� immob_structure ��.
  </code></pre>