Log a warning when client omits User Properties due to packet size over limit

[MicWalter]

Problem or use case

As in accordance with the spec the client omits the User Properties(UP) if adding them would increase the packet size over the allowed limit set by the server. The current problem is that this happens silently and there is no way to inform the user that the UPs were omitted.

One example from spec:

The sender MUST NOT send this property if it would increase the size of the DISCONNECT packet beyond the Maximum Packet Size specified by the receiver [MQTT-3.14.2-4]

Preferred solution or suggestions

Simplest solution: Add a WARN log when the client omits the UPs.