introduce API-VERSION header

Pilz.Net/Api/ApiServer.cs

@@ -1,6 +1,5 @@
 using Castle.Core.Logging;
 using Pilz.Data;
-using Pilz.Extensions.Collections;
 using Pilz.Extensions.Reflection;
 using System.Diagnostics.CodeAnalysis;
 using System.Net;
@@ -34,33 +33,21 @@ public class ApiServer : IApiServer
     public event DataManagerEventHandler? OnResetDataManager;
 
     protected record PrivateParameterInfo(string Name, int Index);
-
     protected record PrivateMessageHandler(string Url, bool UseRegEx, Delegate Handler, PrivateParameterInfo[] Parameters, ApiMessageHandlerAttribute Attribute);
-
     protected record PrivateApiResult(ApiResult Original, object? ResultContent);
 
     public string ApiUrl { get; }
-
+    public uint ApiVersion { get; set; } = 1;
     public virtual bool EnableAuth { get; set; }
-
     public IApiMessageSerializer Serializer { get; set; } = new DefaultApiMessageSerializer();
-
     public ILogger Log { get; set; } = NullLogger.Instance;
-
     public bool DebugMode { get; set; }
-
     public bool AllowMultipleRequests { get; set; }
-
     public int StopDelay { get; set; } = 5000;
-
     public bool AutoRestartOnError { get; set; } = true;
-
     public int MaxAutoRestartsPerMinute { get; set; } = 10;
-
     public int MaxConcurentConnections { get; set; } = 5;
-
     public IDataManager Manager => GetManager();
-
     public bool ThreadedDataManager { get; set; }
 
     public ApiServer(string apiUrl) : this(apiUrl, null)
@@ -450,6 +437,10 @@ public class ApiServer : IApiServer
             return;
         }
 
+        // Set response header
+        Log.Debug("Set response headers");
+        context.Response.AppendHeader("API-VERSION", ApiVersion.ToString());
+
         // Set response parameters
         Log.Debug("Set response parameters");
         context.Response.StatusCode = (int)result.Original.StatusCode;