@Test
    fun `find by id and user id should return the saved User`() {
        val user = createUser(1)
        assertThat(user.id).isZero()

        userRepository.saveAndFlush(user1)
        assertThat(user.id).isPositive()
        // ...
}

    private fun createUser(userId: Long): User = User(
            userId = userId.toString(),
            personId = 456L,
            username = "username")

@Entity
data class User(
        @Id
        @SequenceGenerator(name = "users_id_generator", sequenceName = "users_id_seq")
        @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "users_id_generator")
        val id: Long = 0,
        @NaturalId
        val userId: String
}