code: def create_user(self, myshopify_domain, password=None):
          
          if not myshopify_domain:
              raise ValueError('ShopUsers must have a myshopify domain')
  
          user = self.model(myshopify_domain=myshopify_domain)
  
          # Never want to be able to log on externally.
          # Authentication will be taken care of by Shopify OAuth.
          user.set_unusable_password()
          user.save(using=self._db)
          return user
docs: Creates and saves a ShopUser with the given domain and password.