Add constraint on periodic report dates

Author: bryanjnelson

dbschema/periodic-report.gel

@@ -3,6 +3,7 @@ module default {
     required period: range<cal::local_date>;
     `start` := range_get_lower(.period);
     `end` := date_range_get_upper(.period);
+    constraint expression on (.`end` >= .`start`);
 
     skippedReason: str;