witness (un)register: add event details

Also create an actual event notification for both actions, rather
than just creating the event record.

This is presumably an oversight from the original conversion to
repmgr4 which no-one has noticed before.

repmgr-action-witness.c

@@ -371,13 +371,24 @@ do_witness_register(void)
 		exit(ERR_BAD_CONFIG);
 	}
 
-	/* create event */
-	create_event_record(primary_conn,
-						&config_file_options,
-						config_file_options.node_id,
-						"witness_register",
-						true,
-						NULL);
+	{
+		PQExpBufferData event_details;
+		initPQExpBuffer(&event_details);
+
+		appendPQExpBuffer(&event_details,
+						  _("witness registration succeeded; upstream node ID is %i"),
+						  node_record.upstream_node_id);
+
+		/* create event */
+		create_event_notification(primary_conn,
+								  &config_file_options,
+								  config_file_options.node_id,
+								  "witness_register",
+								  true,
+								  event_details.data);
+
+		termPQExpBuffer(&event_details);
+	}
 
 	PQfinish(primary_conn);
 	PQfinish(witness_conn);
@@ -520,13 +531,24 @@ do_witness_unregister(void)
 		exit(ERR_BAD_CONFIG);
 	}
 
-	/* Log the event */
-	create_event_record(primary_conn,
-						&config_file_options,
-						witness_node_id,
-						"witness_unregister",
-						true,
-						NULL);
+
+	{
+		PQExpBufferData event_details;
+		initPQExpBuffer(&event_details);
+
+		appendPQExpBufferStr(&event_details,
+							 _("witness unregistration succeeded"));
+
+		/* create event */
+		create_event_notification(primary_conn,
+								  &config_file_options,
+								  witness_node_id,
+								  "witness_unregister",
+								  true,
+								  event_details.data);
+
+		termPQExpBuffer(&event_details);
+	}
 
 	PQfinish(primary_conn);