Added the current connection information test url option

https://github.com/2dust/v2rayN/discussions/7268

v2rayN/ServiceLib/Handler/ConnectionHandler.cs

@@ -0,0 +1,42 @@
+namespace ServiceLib.Handler;
+
+public class ConnectionHandler
+{
+    private static readonly Lazy<ConnectionHandler> _instance = new(() => new());
+    public static ConnectionHandler Instance => _instance.Value;
+
+    public async Task<string> RunAvailabilityCheck()
+    {
+        var downloadHandle = new DownloadService();
+        var time = await downloadHandle.RunAvailabilityCheck(null);
+        var ip = time > 0 ? await GetIPInfo(downloadHandle) ?? Global.None : Global.None;
+
+        return string.Format(ResUI.TestMeOutput, time, ip);
+    }
+
+    private async Task<string?> GetIPInfo(DownloadService downloadHandle)
+    {
+        var url = AppHandler.Instance.Config.SpeedTestItem.IPAPIUrl;
+        if (url.IsNullOrEmpty())
+        {
+            return null;
+        }
+
+        var result = await downloadHandle.TryDownloadString(url, true, "");
+        if (result == null)
+        {
+            return null;
+        }
+
+        var ipInfo = JsonUtils.Deserialize<IPAPIInfo>(result);
+        if (ipInfo == null)
+        {
+            return null;
+        }
+
+        var ip = ipInfo.ip ?? ipInfo.clientIp ?? ipInfo.ip_addr ?? ipInfo.query;
+        var country = ipInfo.country_code ?? ipInfo.country ?? ipInfo.countryCode ?? ipInfo.location?.country_code;
+
+        return $"({country ?? "unknown"}) {ip}";
+    }
+}