public List<AuthzRoleDTO> findByIds(Collection<String> ids) {
        return asImmutableList(db.find(DBQuery.in("_id", ids)));
    }
@Test
    void findByIds() {
        final List<AuthzRoleDTO> roles = service.findByIds(ImmutableSet.of(
                "5d41bb973086a840541a3ed2",
                "564c6707c8306e079f718980"
        ));

        assertThat(roles).hasSize(2);

        assertThat(roles.get(0).id()).isEqualTo("564c6707c8306e079f718980");
        assertThat(roles.get(0).name()).isEqualTo("Reader");

        assertThat(roles.get(1).id()).isEqualTo("5d41bb973086a840541a3ed2");
        assertThat(roles.get(1).name()).isEqualTo("Alerts Manager");
    }