Mention #13541 #13542 #13549 13551 in release notes

References #13537.

Author: michaelklishin

release-notes/4.1.0.md

@@ -25,6 +25,20 @@ for the complete list of related changes.
 
 ## Breaking Changes and Compatibility Notes
 
+### Initial AMQP 0-9-1 Maximum Frame Size
+
+Before a client connection can negotiate a maximum frame size (`frame_max`), it must authenticate
+successfully. Before the authenticated phase, a special lower `frame_max` value
+is used.
+
+With this release, the value was increased from the original 4096 bytes to 8192
+to accommodate larger [JWT tokens](https://www.rabbitmq.com/docs/oauth2).
+
+Clients that do override `frame_max` now must use values of 8192 bytes or greater.
+We recommend using the default server value of `131072`: do not override the `frame_max`
+key in `rabbitmq.conf` and do not set it in the application code.
+
+
 ### MQTT
 
  * The default MQTT [Maximum Packet Size](https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-v5.0-os.html#_Toc3901086) changed from 256 MiB to 16 MiB.