Add Dynamic DNS support

BTCPayServer/Models/ServerViewModels/DynamicDnsViewModel.cs

@@ -0,0 +1,43 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using System.Linq;
+using System.Threading.Tasks;
+using BTCPayServer.Services;
+
+namespace BTCPayServer.Models.ServerViewModels
+{
+    public class DynamicDnsViewModel
+    {
+        public class WellKnownService
+        {
+            public WellKnownService(string name, string url)
+            {
+                Name = name;
+                Url = url;
+            }
+            public string Name { get; set; }
+            public string Url { get; set; }
+        }
+
+        public DynamicDnsSettings Settings { get; set; }
+        public string LastUpdated
+        {
+            get
+            {
+                if (Settings?.LastUpdated is DateTimeOffset date)
+                {
+                    return Views.ViewsRazor.ToTimeAgo(date);
+                }
+                return null;
+            }
+        }
+        public WellKnownService[] KnownServices { get; set; } = new []
+        {
+            new WellKnownService("noip", "https://dynupdate.no-ip.com/nic/update"),
+            new WellKnownService("dyndns", "https://members.dyndns.org/v3/update"),
+            new WellKnownService("duckdns", "https://www.duckdns.org/v3/update"),
+            new WellKnownService("google", "https://domains.google.com/nic/update"),
+        };
+    }
+}