Implemented a new dialog for account re-ordering and required apis.

Wino.Mail/Dialogs/AccountReorderDialog.xaml.cs

@@ -0,0 +1,52 @@
+using System.Collections.ObjectModel;
+using System.Linq;
+using Microsoft.Extensions.DependencyInjection;
+using Windows.UI.Xaml.Controls;
+using Wino.Core.Domain.Interfaces;
+
+namespace Wino.Dialogs
+{
+    public sealed partial class AccountReorderDialog : ContentDialog
+    {
+        public ObservableCollection<IAccountProviderDetailViewModel> Accounts { get; }
+
+        private int count;
+        private bool isOrdering = false;
+
+        private readonly IAccountService _accountService = App.Current.Services.GetService<IAccountService>();
+
+        public AccountReorderDialog(ObservableCollection<IAccountProviderDetailViewModel> accounts)
+        {
+            Accounts = accounts;
+
+            count = accounts.Count;
+
+            InitializeComponent();
+        }
+
+        private void DialogOpened(ContentDialog sender, ContentDialogOpenedEventArgs args)
+        {
+            Accounts.CollectionChanged -= AccountsChanged;
+            Accounts.CollectionChanged += AccountsChanged;
+        }
+
+        private void DialogClosed(ContentDialog sender, ContentDialogClosedEventArgs args) => Accounts.CollectionChanged -= AccountsChanged;
+
+        private async void AccountsChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
+        {
+            if (count - 1 == Accounts.Count)
+                isOrdering = true;
+
+            if (count == Accounts.Count && isOrdering)
+            {
+                // Order is completed. Apply changes.
+
+                var dict = Accounts.ToDictionary(a => a.StartupEntityId, a => Accounts.IndexOf(a));
+
+                await _accountService.UpdateAccountOrdersAsync(dict);
+
+                isOrdering = false;
+            }
+        }
+    }
+}