docs: def get_profile_user_fieldname(profile_model=None, user_model=None):
      """
      Returns the name of the first field on the profile model that
      points to the ``auth.User`` model.
      """
      Profile = profile_model or get_profile_model()
      User = user_model or get_user_model()
      for field in Profile._meta.fields:
          if field.rel and field.rel.to == User:
              return field.name
      raise ImproperlyConfigured("Value for ACCOUNTS_PROFILE_MODEL does not "
                                 "contain a ForeignKey field for auth.User: %s"
                                 % Profile.__name__)