Update documentation for notifications in HA cluster

refs #6203

doc/4-monitoring-remote-systems.md

@@ -674,6 +674,9 @@ Selected features (such as [DB IDO](#high-availability-db-ido)) will only be
 active on the current active master.
 All other passive nodes will pause the features without reload/restart.
 
+Checks and notifications are load-balanced between nodes in the high availability
+zone.
+
 Connections from other zones will be accepted by all active and passive nodes
 but all are forwarded to the current active master dealing with the check results,
 commands, etc.

doc/6-configuring-icinga-2.md

@@ -1556,6 +1556,13 @@ Example:
 
     object NotificationComponent "notification" { }
 
+Attributes:
+
+  Name            |Description
+  ----------------|----------------
+  enable_ha       |**Optional.** Enable the high availability functionality. Only valid in a [cluster setup](#high-availability). Defaults to "true".
+
+
 Can be enabled/disabled using
 
     # icinga2-enable-feature notification