Checkout v2: Improve expired paid partial state (#4827)

Co-authored-by: Andrew Camilleri <evilkukka@gmail.com>

BTCPayServer.Client/Models/StoreBaseData.cs

@@ -16,6 +16,8 @@ namespace BTCPayServer.Client.Models
 
         public string Website { get; set; }
 
+        public string SupportUrl { get; set; }
+
         [JsonConverter(typeof(TimeSpanJsonConverter.Seconds))]
         [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
         public TimeSpan InvoiceExpiration { get; set; } = TimeSpan.FromMinutes(15);