Make it possible to repeatedly apply DB upgrade 11.

Even though this makes PostgreSQL 14 a hard dependency.

etc/db/upgrades/upgrade11-v0.2.1-new-event-log-schema.sql

@@ -6,6 +6,9 @@
 --
 -- ENSURE YOU HAVE BACKED UP THE DATABASE BEFORE RUNNING THIS SCRIPT.
 --
+-- REQUIRES POSTGRESQL VERSION 14 OR NEWER
+-- (Because of CREATE OR REPLACE TRIGGER)
+--
 --
 -- NOTE: This upgrade affects all schemas in the database.
 -- NOTE: Each application starts a transaction, which must be committed
@@ -126,7 +129,7 @@ BEGIN
 
 
 	-- The public.notify() trigger to alert clients that something has changed
-	CREATE TRIGGER event_log_full_notify_tg
+	CREATE OR REPLACE TRIGGER event_log_full_notify_tg
 	AFTER INSERT OR DELETE OR UPDATE
 	ON event_log_full FOR EACH ROW EXECUTE FUNCTION public.notify('event');