Separation of core library from the UWP app.

Wino.Core.Domain/MenuItems/MergedAccountMenuItem.cs

@@ -0,0 +1,44 @@
+using System.Collections.Generic;
+using System.Linq;
+using CommunityToolkit.Mvvm.ComponentModel;
+using Wino.Core.Domain.Entities.Mail;
+using Wino.Core.Domain.Entities.Shared;
+using Wino.Core.Domain.Interfaces;
+
+namespace Wino.Core.Domain.MenuItems
+{
+    public partial class MergedAccountMenuItem : MenuItemBase<MergedInbox, IMenuItem>, IMergedAccountMenuItem
+    {
+        public int MergedAccountCount => HoldingAccounts?.Count() ?? 0;
+
+        public IEnumerable<MailAccount> HoldingAccounts { get; }
+
+        [ObservableProperty]
+        private int unreadItemCount;
+
+        [ObservableProperty]
+        private double synchronizationProgress;
+
+        [ObservableProperty]
+        private string mergedAccountName;
+
+        [ObservableProperty]
+        private bool _isEnabled = true;
+
+        public MergedAccountMenuItem(MergedInbox mergedInbox, IEnumerable<MailAccount> holdingAccounts, IMenuItem parent) : base(mergedInbox, mergedInbox.Id, parent)
+        {
+            MergedAccountName = mergedInbox.Name;
+            HoldingAccounts = holdingAccounts;
+        }
+
+        public void RefreshFolderItemCount()
+        {
+            UnreadItemCount = SubMenuItems.OfType<IAccountMenuItem>().Sum(a => a.UnreadItemCount);
+        }
+
+        public void UpdateAccount(MailAccount account)
+        {
+
+        }
+    }
+}