Method GetTreeGroupBySqlPreviewAsync<TProps>(TreeQueryContext<TProps>, IEnumerable<GroupFieldRequest>, IEnumerable<AggregateRequest>)

SQL Preview for Tree GroupBy (DRY - same SQL as Execute)

public override Task<string> GetTreeGroupBySqlPreviewAsync<TProps>(TreeQueryContext<TProps> context, IEnumerable<GroupFieldRequest> groupFields, IEnumerable<AggregateRequest> aggregations) where TProps : class, new()