Report unauthorized subscription

[ygoe]

Describe the feature request

The public MQTT broker on broker.emqx.io doesn't allow subscribing to #. The client MQTTX tells me after I try that it has failed because I'm not authorized to do that. MQTTnet doesn't tell me. I've looked around for any members of the result object or the client itself but couldn't find anything and no exception is thrown. The subscription was apparently successful but I receive no data after that.

Which project is your feature request related to?

MQTTnet's MqttClient class, I guess, or anywhere, I don't know what you mean.

Describe the solution you'd like

Best would be an exception or some information in the MqttClientSubscribeResult class.

Describe alternatives you've considered

N/A

Additional context