v3.0.3

• [Core] Fixed issues in MQTTv5 message encoding and decoding.
• [Core] Added extension method to allow usage of WebSocket4Net in clients to fix issues with AWS and Xamarin.
• [Core] Fixed usage of wrong data type for passwords (string -> byte[]).
• [Core] Fixed an ObjectDisposedException when sending data using a WebSocket channel.
• [Core] Performance optimizations.
• [Client] Added support for extended authentication exchange.
• [Client] Exposed MQTTv5 CONNACK values to client.
• [Client] Added MqttClientSubscribeOptionsBuilder.
• [Client] The disconnected handler is now executed in a new task to prevent deadlocks when reconnecting etc. (thanks to @lizziebeans).
• [Client] Converted option DualMode into nullable boolean to preserve original value and avoid exceptions in IPv4 only networks (thanks to @lavaflo).
• [Server] Exposed ClientCertificateRequired and CheckCertificateRevocation at TLS options.
• [Server] Exposed client certificate at client connection validator.
• [Server] The subscription interceptor now supports altering the entire topic filter.
• [Server] Exposed more properties to the connection validator context.
• [MQTTnet.Server] Added authentication support via Python script file.
• [MQTTnet.Server] Migrated the result of connection validations to ReasonCode (MQTTv5) instead of ReturnCode (MQTTv3 only) (BREAKING CHANGE!).