pleroma: add webfinger address and instance

Pleroma/Models/Account.cs

@@ -41,7 +41,25 @@ public class Account
     [JsonPropertyName("username")]
     public string Username { get; set; } = null!;
 
-    public override string ToString() => $"@{Username}";
+    [JsonPropertyName("acct")]
+    public string Webfinger { get; set; } = null!;
+
+    public string? Instance
+    {
+        get
+        {
+            if (Webfinger == null)
+                return null;
+
+            int spl = Webfinger.IndexOf('@');
+            if (spl == -1)
+                return null;
+
+            return Webfinger[(spl + 1)..];
+        }
+    }
+
+    public override string ToString() => $"@{Webfinger}";
 }
 
 [JsonConverter(typeof(AccountIDConverter))]