hydra-queue-runner: Detect changes to the scheduling shares

src/sql/upgrade-41.sql

@@ -0,0 +1,5 @@
+create function notifyJobsetSharesChanged() returns trigger as 'begin notify jobset_shares_changed; return null; end;' language plpgsql;
+create trigger JobsetSharesChanged after update on Jobsets for each row
+  when (old.schedulingShares != new.schedulingShares) execute procedure notifyJobsetSharesChanged();
+
+alter table Jobsets add constraint jobsets_check check (schedulingShares > 0);