AuthenticationServiceException example

        // No user has been found via the $this->userLoader callback         if (null === $user) {
            $exception = new UserNotFoundException();
            $exception->setUserIdentifier($this->userIdentifier);

            throw $exception;
        }

        if (!$user instanceof UserInterface) {
            throw new AuthenticationServiceException(sprintf('The user provider must return a UserInterface object, "%s" given.', get_debug_type($user)));
        }

        return $this->user = $user;
    }

    public function getUserLoader(): ?callable
    {
        return $this->userLoader;
    }

    public function setUserLoader(callable $userLoader): void
    {