Method GroupByRedb<TKey>(Expression<Func<IRedbObject, TKey>>)

Group by IRedbObject base fields (id, scheme_id, parent_id, etc.).
Uses IRedbObject for compile-time safety - Props not visible!

IRedbGroupedQueryable<TKey, TProps> GroupByRedb<TKey>(Expression<Func<IRedbObject, TKey>> keySelector)