Base64 subscription fetcher works, some ui changes

WinWARP.Core/Services/Interfaces/IDialogService.cs

@@ -8,4 +8,5 @@ namespace WinWARP.Core.Services.Interfaces;
 public interface IDialogService
 {
     Task<(CommonDialogResult Result, string Title, string URL, int UpdateInterval)> ShowAddSubscriptionAsync();
+    Task ShowErrorAsync(string message);
 }

WinWARP.Core/Services/Interfaces/ISubscriptionFetcher.cs

@@ -9,4 +9,5 @@ public interface ISubscriptionFetcher
 {
     public bool IsUrlValid(string url);
     public Task<Subscription> FetchAsync(string url);
+    public List<string> GetTags(string connectionString);
 }