safe Useragent as string and export settings after changing

Tranga/MangaConnectors/HttpDownloadClient.cs

@@ -14,10 +14,7 @@ internal class HttpDownloadClient : DownloadClient
 
     public HttpDownloadClient(GlobalBase clone, Dictionary<byte, int> rateLimitRequestsPerMinute) : base(clone, rateLimitRequestsPerMinute)
     {
-        if (settings.customUserAgent is null || settings.customUserAgent.Length < 1)
+        Client.DefaultRequestHeaders.TryAddWithoutValidation("User-Agent", settings.userAgent);
-            Client.DefaultRequestHeaders.UserAgent.Add(new ProductInfoHeaderValue("Tranga", "1.0"));
-        else
-            Client.DefaultRequestHeaders.TryAddWithoutValidation("User-Agent", settings.customUserAgent);
     }
     
     protected override RequestResult MakeRequestInternal(string url, string? referrer = null, string? clickButton = null)

Tranga/Server.cs

@@ -200,6 +200,9 @@ public class Server : GlobalBase
             case "Settings":
                 SendResponse(HttpStatusCode.OK, response, settings);
                 break;
+            case "Settings/userAgent":
+                SendResponse(HttpStatusCode.OK, response, settings.userAgent);
+                break;
             case "NotificationConnectors":
                 SendResponse(HttpStatusCode.OK, response, notificationConnectors);
                 break;
@@ -384,13 +387,13 @@ public class Server : GlobalBase
                 settings.UpdateWorkingDirectory(workingDirectory);
                 SendResponse(HttpStatusCode.Accepted, response);
                 break;*/
-            case "Settings/customUserAgent":
+            case "Settings/userAgent":
                 if(!requestVariables.TryGetValue("userAgent", out string? customUserAgent))
                 {
                     SendResponse(HttpStatusCode.BadRequest, response);
                     break;
                 }
-                settings.customUserAgent = customUserAgent;
+                settings.UpdateUserAgent(customUserAgent);
                 SendResponse(HttpStatusCode.Accepted, response);
                 break;
             case "Settings/customRequestLimit":

Tranga/TrangaSettings.cs

@@ -1,4 +1,5 @@
-using System.Runtime.InteropServices;
+using System.Net.Http.Headers;
+using System.Runtime.InteropServices;
 using Newtonsoft.Json;
 using Tranga.LibraryConnectors;
 using Tranga.NotificationConnectors;
@@ -12,7 +13,9 @@ public class TrangaSettings
     public string workingDirectory { get; private set; }
     public int apiPortNumber { get; init; }
     public string styleSheet { get; private set; }
-    public string? customUserAgent { get; set; } = null;
+
+    public string userAgent { get; set; } =
+        $"Tranga ({Enum.GetName(Environment.OSVersion.Platform)}; {(Environment.Is64BitOperatingSystem ? "x64" : "")}) / 1.0";
     [JsonIgnore] public string settingsFilePath => Path.Join(workingDirectory, "settings.json");
     [JsonIgnore] public string libraryConnectorsFilePath => Path.Join(workingDirectory, "libraryConnectors.json");
     [JsonIgnore] public string notificationConnectorsFilePath => Path.Join(workingDirectory, "notificationConnectors.json");
@@ -120,6 +123,12 @@ public class TrangaSettings
         ExportSettings();
     }
 
+    public void UpdateUserAgent(string customUserAgent)
+    {
+        this.userAgent = customUserAgent;
+        ExportSettings();
+    }
+
     public void ExportSettings()
     {
         if (File.Exists(settingsFilePath))