pub fn plan_insert_query(
    scx: &StatementContext<'_>,
    table_name: ResolvedItemName,
    columns: Vec<Ident>,
    source: InsertSource<Aug>,
    returning: Vec<SelectItem<Aug>>
) -> Result<(GlobalId, HirRelationExpr, PlannedRootQuery<Vec<HirScalarExpr>>), PlanError>