Session Present Flag is not respected

[lizhanhui]

MQTT protocol defines Session Present Flag as follows:

ConnectHandler writes ConnAck having session-present=false constantly:

See:

rocketmq-mqtt/mqtt-cs/src/main/java/org/apache/rocketmq/mqtt/cs/protocol/mqtt/handler/MqttConnectHandler.java

Line 109 in 477d478

channel.writeAndFlush(mqttConnAckMessage);

rocketmq-mqtt/mqtt-cs/src/main/java/org/apache/rocketmq/mqtt/cs/protocol/mqtt/facotry/MqttMessageFactory.java

Line 42 in 477d478

public static MqttConnAckMessage buildConnAckMessage(MqttConnectReturnCode returnCode) {

[DongyuanPan]

Yes, currently there's no storage for subscription relationships, meaning it doesn't support cleansession=false. Therefore, the default setting is false