A necessary party is one without whom “complete relief cannot be accorded among those already parties” and/or whose absence would “leave any of the persons already parties subject to a substantial risk of incurring double, multiple, or otherwise inconsistent obligations by reason of [the non-party’s] claimed interest.” (Code of Civ. Proc., § 389(a); Olszewski v. Scripps Health (2003) 30 Cal.4th 798, 808-809.)