Will payload can be set above 65.535 bytes

[MicWalter]

Expected behavior

As the spec states the Will publish payload is binary data (max 65.535 bytes), so the client should check if I set a payload higher than that.

Actual behavior

It is possible to exceed the binary data limit if I create a Mqtt5Publish and extend it as will. This breaks the encoding of the Connect packet.

To Reproduce

Reproducer code

 final @NotNull byte[] bytes = MqttCommonUtil.randomBytes(80_000);
        //throws error because payload exceeds binary data length 65_535
//        final Mqtt5WillPublish test = Mqtt5WillPublish.builder().topic("test").payload(bytes).build();

        //doesn't throw error because payload is not treated as binary data
        final Mqtt5Publish mqtt5Publish = Mqtt5Publish.builder().topic("test").payload(bytes).build();
        final Mqtt5WillPublish test2 = mqtt5Publish.extend().asWill().delayInterval(10).build();

        final Mqtt5AsyncClient retClient2 = Mqtt5Client.builder()
                .identifier("retsub")
                .simpleAuth().username("test").applySimpleAuth()
                .willPublish(test2).buildAsync();
        retClient2.connect().get();

Details

• Affected HiveMQ MQTT Client version(s):
• Used JVM version: