Parse records and keyed collection queries

example/expensive_order.delta

@@ -0,0 +1,13 @@
+type order = {
+  customer : string;
+  total : int;
+}
+
+input orders : collection order
+
+let tax n = n * 20 / 100
+
+query expensive_orders =
+  orders
+  |> filter (fun o -> o.total > 1000)
+  |> map (fun o -> (o.customer, tax o.total))