Client ID change alert

Author: PatAltimore

articles/iot-operations/connect-to-cloud/howto-configure-mqtt-endpoint.md

@@ -747,7 +747,10 @@ kubectl create configmap client-ca-configmap --from-file root_ca.crt -n azure-io
 
 ### Client ID prefix
 
-You can set a client ID prefix for the MQTT client. The client ID is generated by appending the dataflow instance name to the prefix.
+You can set a client ID prefix for the MQTT client. The client ID is generated by appending the dataflow instance name to the prefix. 
+
+> [!CAUTION]
+> Most applications should not modify the client ID prefix. Don't modify this after an initial IoT Operations deployment. Changing the client ID prefix after deployment might result in data loss.
 
 # [Portal](#tab/portal)