Replace custom socket implementation with SignalR.

Replace MSAL and custom cookie auth with Microsoft.Identity.EntityFramework
Also some UI redesign to accommodate different login experience.

Shogi.Contracts/Types/Session.cs

@@ -1,9 +1,20 @@
-namespace Shogi.Contracts.Types;
+using System;
+
+namespace Shogi.Contracts.Types;
 
 public class Session
 {
-	public User Player1 { get; set; }
-	public User? Player2 { get; set; }
-	public string SessionName { get; set; }
+	/// <summary>
+	/// Email
+	/// </summary>
+	public string Player1 { get; set; }
+
+	/// <summary>
+	/// Email. Null if no second player exists.
+	/// </summary>
+	public string? Player2 { get; set; }
+
+	public Guid SessionId { get; set; }
+
 	public BoardState BoardState { get; set; }
 }

Shogi.Contracts/Types/SessionMetadata.cs

@@ -1,8 +1,11 @@
-namespace Shogi.Contracts.Types
+using System;
+
+namespace Shogi.Contracts.Types
 {
-  public class SessionMetadata
-  {
-    public string Name { get; set; }
-    public int PlayerCount { get; set; }
-  }
+	public class SessionMetadata
+	{
+		public Guid SessionId { get; set; }
+		public string Player1 { get; set; } = string.Empty;
+		public string Player2 { get; set; } = string.Empty;
+	}
 }

Shogi.Contracts/Types/SocketAction.cs

@@ -1,9 +0,0 @@
-namespace Shogi.Contracts.Types
-{
-  public enum SocketAction
-  {
-    SessionCreated,
-    SessionJoined,
-    PieceMoved
-  }
-}

Shogi.Contracts/Types/User.cs

@@ -1,17 +0,0 @@
-namespace Shogi.Contracts.Types;
-
-public class User
-{
-    public string Id { get; set; } = string.Empty;
-
-    /// <summary>
-    /// A display name for the user.
-    /// </summary>
-    public string Name { get; set; } = string.Empty;
-
-    public User(string id, string name)
-    {
-        Id = id;
-        Name = name;
-    }
-}