Fix some minor TODOs.

Source/MQTTnet.Server/Mqtt/MqttApplicationMessageInterceptor.cs

@@ -46,21 +46,5 @@ namespace MQTTnet.Server.Mqtt
 
             return Task.CompletedTask;
         }
-
-        // TODO: Create dump(object) method in wrapper (creates JSON and prints it).
-        public class PythonMqttApplicationMessageInterceptorContext
-        {
-            public bool accept_connection;
-
-            public bool accept_publish;
-
-            public string client_id;
-
-            public string topic;
-
-            public int qos;
-
-            public bool retain;
-        }
     }
 }

Source/MQTTnet/Formatter/IMqttDataConverter.cs

@@ -12,6 +12,8 @@ namespace MQTTnet.Formatter
     {
         MqttPublishPacket CreatePublishPacket(MqttApplicationMessage applicationMessage);
 
+        MqttPubAckPacket CreatePubAckPacket(MqttPublishPacket publishPacket);
+
         MqttApplicationMessage CreateApplicationMessage(MqttPublishPacket publishPacket);
 
         MqttClientAuthenticateResult CreateClientConnectResult(MqttConnAckPacket connAckPacket);

Source/MQTTnet/Formatter/MqttPacketWriter.cs

@@ -19,7 +19,6 @@ namespace MQTTnet.Formatter
         public static int InitialBufferSize = 128;
         public static int MaxBufferSize = 4096;
 
-        // TODO: Consider using the ArrayPool here together with FreeBuffer.
         private byte[] _buffer = new byte[InitialBufferSize];
 
         private int _offset;

Source/MQTTnet/Formatter/V3/MqttV310DataConverter.cs

@@ -33,6 +33,15 @@ namespace MQTTnet.Formatter.V3
             };
         }
 
+        public MqttPubAckPacket CreatePubAckPacket(MqttPublishPacket publishPacket)
+        {
+            return new MqttPubAckPacket
+            {
+                PacketIdentifier = publishPacket.PacketIdentifier,
+                ReasonCode = MqttPubAckReasonCode.Success
+            };
+        }
+
         public MqttApplicationMessage CreateApplicationMessage(MqttPublishPacket publishPacket)
         {
             if (publishPacket == null) throw new ArgumentNullException(nameof(publishPacket));

Source/MQTTnet/Formatter/V5/MqttV500DataConverter.cs

@@ -46,6 +46,15 @@ namespace MQTTnet.Formatter.V5
             return packet;
         }
 
+        public MqttPubAckPacket CreatePubAckPacket(MqttPublishPacket publishPacket)
+        {
+            return new MqttPubAckPacket
+            {
+                PacketIdentifier = publishPacket.PacketIdentifier,
+                ReasonCode = MqttPubAckReasonCode.Success
+            };
+        }
+
         public MqttApplicationMessage CreateApplicationMessage(MqttPublishPacket publishPacket)
         {
             return new MqttApplicationMessage
@@ -180,12 +189,10 @@ namespace MQTTnet.Formatter.V5
 
         public MqttClientPublishResult CreatePublishResult(MqttPubAckPacket pubAckPacket)
         {
-            var result = new MqttClientPublishResult();
-
-            if (pubAckPacket?.ReasonCode != null)
+            var result = new MqttClientPublishResult
             {
-                result.ReasonCode = (MqttClientPublishReasonCode)pubAckPacket.ReasonCode;
-            }
+                ReasonCode = (MqttClientPublishReasonCode)pubAckPacket.ReasonCode
+            };
 
             return result;
         }

Source/MQTTnet/Formatter/V5/MqttV500PacketEncoder.cs

@@ -285,7 +285,7 @@ namespace MQTTnet.Formatter.V5
 
             if (!packet.ReasonCode.HasValue)
             {
-                throw new MqttProtocolViolationException("PubAck packet must contain a connect reason.");
+                throw new MqttProtocolViolationException("PubAck packet must contain a reason code.");
             }
 
             packetWriter.Write(packet.PacketIdentifier.Value);

Source/MQTTnet/Server/MqttClientConnection.cs

@@ -330,15 +330,8 @@ namespace MQTTnet.Server
             var applicationMessage = _dataConverter.CreateApplicationMessage(publishPacket);
             _sessionsManager.DispatchApplicationMessage(applicationMessage, this);
 
-            // TODO: Create ACK packet.
-            
-            var response = new MqttPubAckPacket
-            {
-                PacketIdentifier = publishPacket.PacketIdentifier,
-                ReasonCode = MqttPubAckReasonCode.Success
-            };
-
-            return SendAsync(response);
+            var pubAckPacket = _dataConverter.CreatePubAckPacket(publishPacket);
+            return SendAsync(pubAckPacket);
         }
 
         private Task HandleIncomingPublishPacketWithQoS2Async(MqttPublishPacket publishPacket)