public List<UserDTO> usersToUserDTOs(List<User> users) {
        return users.stream().filter(Objects::nonNull).map(this::userToUserDTO).toList();
    }
@Test
    void usersToUserDTOsShouldMapOnlyNonNullUsers() {
        List<User> users = new ArrayList<>();
        users.add(user);
        users.add(null);

        List<UserDTO> userDTOS = userMapper.usersToUserDTOs(users);

        assertThat(userDTOS).isNotEmpty().size().isEqualTo(1);
    }