Big refactory on session management:

- introduced a unique point of access and management of sessions state (SessionRepository)
- separated behaiour for sessions with clean flag to false into DurableSession
- separated behaviour for session with clean flag to true into TransientSession

broker/src/main/java/io/moquette/spi/impl/MessagesPublisher.java

@@ -19,7 +19,6 @@ package io.moquette.spi.impl;
 import io.moquette.server.ConnectionDescriptorStore;
 import io.moquette.spi.ClientSession;
 import io.moquette.spi.IMessagesStore;
-import io.moquette.spi.ISessionsStore;
 import io.moquette.spi.impl.subscriptions.ISubscriptionsDirectory;
 import io.moquette.spi.impl.subscriptions.Subscription;
 import io.moquette.spi.impl.subscriptions.Topic;
@@ -27,23 +26,26 @@ import io.netty.buffer.ByteBuf;
 import io.netty.handler.codec.mqtt.*;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+
 import java.util.List;
+
 import static io.moquette.spi.impl.ProtocolProcessor.lowerQosToTheSubscriptionDesired;
 
 class MessagesPublisher {
 
     private static final Logger LOG = LoggerFactory.getLogger(MessagesPublisher.class);
     private final ConnectionDescriptorStore connectionDescriptors;
-    private final ISessionsStore m_sessionsStore;
     private final PersistentQueueMessageSender messageSender;
     private final ISubscriptionsDirectory subscriptions;
+    private SessionsRepository sessionsRepository;
 
-    public MessagesPublisher(ConnectionDescriptorStore connectionDescriptors, ISessionsStore sessionsStore,
-                             PersistentQueueMessageSender messageSender, ISubscriptionsDirectory subscriptions) {
+    public MessagesPublisher(ConnectionDescriptorStore connectionDescriptors,
+                             PersistentQueueMessageSender messageSender, ISubscriptionsDirectory subscriptions,
+                             SessionsRepository sessionsRepository) {
         this.connectionDescriptors = connectionDescriptors;
-        this.m_sessionsStore = sessionsStore;
         this.messageSender = messageSender;
         this.subscriptions = subscriptions;
+        this.sessionsRepository = sessionsRepository;
     }
 
     static MqttPublishMessage notRetainedPublish(String topic, MqttQoS qos, ByteBuf message) {
@@ -77,7 +79,7 @@ class MessagesPublisher {
 
         for (final Subscription sub : topicMatchingSubscriptions) {
             MqttQoS qos = lowerQosToTheSubscriptionDesired(sub, publishingQos);
-            ClientSession targetSession = m_sessionsStore.sessionForClient(sub.getClientId());
+            ClientSession targetSession = this.sessionsRepository.sessionForClient(sub.getClientId());
 
             boolean targetIsActive = this.connectionDescriptors.isConnected(sub.getClientId());
 //TODO move all this logic into messageSender, which puts into the flightZone only the messages that pull out of the queue.