code: def send_activation(self, user, sender=None, **kwargs):
          
          if user.is_active:
              return False
          token = self.get_token(user)
          kwargs.update({"token": token})
          self.email_message(
              user, self.activation_subject, self.activation_body, sender, **kwargs
          ).send()
docs: Invites a user to join the site