CAMEL-25781: camel-azure-eventhubs - add 4.22.3 upgrade guide note to main

docs/user-manual/modules/ROOT/pages/camel-4x-upgrade-guide-4_22.adoc

@@ -13,6 +13,19 @@ See the xref:camel-upgrade-recipes-tool.adoc[documentation] page for details.
 
 == Upgrading from 4.22.2 to 4.22.3
 
+=== camel-azure-eventhubs - an event that completes when the checkpoint timer of its window has run is checkpointed
+
+With `checkpointBatchTimeout`, the consumer now starts a new checkpoint window when the timer of the current window
+has run, and no longer when the wall clock passes the time the timer was scheduled for. Before, an event that
+completed in the millisecond in which the timer ran (or while the timer was taking the count) was counted in the
+window whose count had already been taken: it was checkpointed only with the next event, and when the partition stayed
+quiet it was delivered again after a restart.
+
+The `CamelAzureEventHubsCheckpointUpdatedBy` header can now be `timeout`. An event that completes after the
+scheduled time of its window, but before the (late) timer has run, joins that window and gets `timeout`; its offset is
+checkpointed by that timer. Before, such an event always started a new window, so `timeout` was practically never
+set. Routes that read this header can now see `timeout` as well as `size`.
+
 === camel-milo - the OPC UA client validates the server certificate
 
 When the endpoint it selects uses a security policy other than `None`, the `milo-client` and `milo-browse` components