new startup process UI for Windows

windows/WinUI/OnboardProcess/LogIn.xaml.cs

@@ -0,0 +1,57 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Data;
+using System.Windows.Documents;
+using System.Windows.Input;
+using System.Windows.Media;
+using System.Windows.Media.Imaging;
+using System.Windows.Navigation;
+using System.Windows.Shapes;
+
+namespace WinUI.OnboardProcess
+{
+    /// <summary>
+    /// Interaction logic for LogIn.xaml
+    /// </summary>
+    public partial class LogIn : UserControl, ISwitchable
+    {
+        public LogIn()
+        {
+            InitializeComponent();
+        }
+
+        public void UtilizeState(object state)
+        {
+            throw new NotImplementedException();
+        }
+
+        public void LoginButton_Click(object sender, RoutedEventArgs e)
+        {
+            DoLogin();
+        }
+
+        public void BackButton_Click(object sender, RoutedEventArgs e)
+        {
+            Switcher.Switch(new RegisterOrLogIn());
+        }
+
+        private async void DoLogin()
+        {
+            CentralAPI api = CentralAPI.Instance;
+            bool didLogIn = await api.Login(EmailAddressTextBox.Text, PasswordTextBox.Password.ToString(), false);
+            if (didLogIn)
+            {
+                Switcher.Switch(new CreateOrJoin());
+            }
+            else
+            {
+                ErrorText.Content = "Invalid username or password";
+            }
+        }
+    }
+}