public SimpleAuthenticationConfig addUser(@Nonnull String username, @Nonnull String password, String... roles) {
        addUser(username, new UserDto(password, roles));
        return self();
    }
@Test
    public void testAddUserWithEmptyPassword() {
        SimpleAuthenticationConfig c = new SimpleAuthenticationConfig();
        assertThrows(IllegalArgumentException.class, () -> c.addUser("user", ""));
        assertThrows(IllegalArgumentException.class, () -> c.addUser("user", (String) null));
    }