public static Index withRelations(String name) {
    return new Index(name, true);
  }
@Test
  public void withRelations_index_name_must_not_contain_upper_case_char() {
    assertThatThrownBy(() -> Index.withRelations("Issues"))
      .isInstanceOf(IllegalArgumentException.class)
      .hasMessage("Index name must be lower-case letters or '_all': Issues");
  }