GuestLog - User message improvements

- Added UserMessageService to have common methods for showing messages and errors to the user.
- Added Result record so services can return status on operation error (so it can be shown in the UI messages).
- Updated services to use the new Result record.
- Updated pages to use the new IUserMessageService.

src/Somnia.GuestLog/Services/IUserMessageService.cs

@@ -0,0 +1,17 @@
+using Somnia.GuestLog.Models.DTOs;
+
+namespace Somnia.GuestLog.Services;
+
+public interface IUserMessageService
+{
+    public void ShowMessage(string text, MessageKind kind, params object[] parameters);
+
+    public void ShowResult(Result resultDto);
+    public void ShowResultWithMessage(Result resultDto, string message);
+
+
+    public enum MessageKind
+    {
+        Info, Warning, Error, Success, Normal
+    }
+}