Initial setup of environment service

Environment/Service/MessageHandler.cs

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+using System.Text.Json;
+using ChrisKaczor.HomeMonitor.Environment.Service.Data;
+using MQTTnet;
+using MQTTnet.Client;
+
+namespace ChrisKaczor.HomeMonitor.Environment.Service;
+
+public class MessageHandler : IHostedService
+{
+    private readonly IConfiguration _configuration;
+    private readonly Database _database;
+    private readonly IMqttClient _mqttClient;
+
+    private readonly MqttFactory _mqttFactory;
+    private readonly string _topic;
+
+    public MessageHandler(IConfiguration configuration, Database database)
+    {
+        _configuration = configuration;
+        _database = database;
+
+        _database.EnsureDatabase();
+
+        _topic = _configuration["Mqtt:Topic"] ?? string.Empty;
+
+        if (string.IsNullOrEmpty(_topic))
+            throw new InvalidOperationException("Topic not set");
+
+        _mqttFactory = new MqttFactory();
+        _mqttClient = _mqttFactory.CreateMqttClient();
+
+        _mqttClient.ApplicationMessageReceivedAsync += OnApplicationMessageReceivedAsync;
+    }
+
+    public async Task StartAsync(CancellationToken cancellationToken)
+    {
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer(_configuration["Mqtt:Server"]).Build();
+        await _mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+
+        var mqttSubscribeOptions = _mqttFactory.CreateSubscribeOptionsBuilder().WithTopicFilter($"{_topic}/#").Build();
+        await _mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);
+    }
+
+    public async Task StopAsync(CancellationToken cancellationToken)
+    {
+        await _mqttClient.DisconnectAsync(new MqttClientDisconnectOptionsBuilder().Build(), CancellationToken.None);
+    }
+
+    private async Task OnApplicationMessageReceivedAsync(MqttApplicationMessageReceivedEventArgs arg)
+    {
+        var topic = arg.ApplicationMessage.Topic;
+        var payload = arg.ApplicationMessage.ConvertPayloadToString();
+
+        WriteLog($"Topic: {topic} = {payload}");
+
+        var message = JsonSerializer.Deserialize<Message>(payload);
+
+        if (message == null)
+            return;
+
+        await _database.StoreMessageAsync(message);
+    }
+
+    private static void WriteLog(string message)
+    {
+        Console.WriteLine(message);
+    }
+}