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.Api/Application/GameHub.cs

@@ -0,0 +1,19 @@
+using Microsoft.AspNetCore.SignalR;
+
+namespace Shogi.Api.Application;
+
+/// <summary>
+/// Used to receive signals from connected clients.
+/// </summary>
+public class GameHub : Hub
+{
+	public Task Subscribe(string sessionId)
+	{
+		return this.Groups.AddToGroupAsync(this.Context.ConnectionId, sessionId);
+	}
+
+	public Task Unsubscribe(string sessionId)
+	{
+		return this.Groups.RemoveFromGroupAsync(this.Context.ConnectionId, sessionId);
+	}
+}

Shogi.Api/Application/GameHubContext.cs

@@ -0,0 +1,21 @@
+using Microsoft.AspNetCore.SignalR;
+
+namespace Shogi.Api.Application;
+
+/// <summary>
+/// Used to send signals to connected clients.
+/// </summary>
+public class GameHubContext(IHubContext<GameHub> context)
+{
+	public async Task Emit_SessionJoined(string sessionId)
+	{
+		var clients = context.Clients.Group(sessionId);
+		await clients.SendAsync("SessionJoined");
+	}
+
+	public async Task Emit_PieceMoved(string sessionId)
+	{
+		var clients = context.Clients.Group(sessionId);
+		await clients.SendAsync("PieceMoved");
+	}
+}

Shogi.Api/Application/ShogiApplication.cs

@@ -0,0 +1,143 @@
+using Microsoft.AspNetCore.Identity;
+using Microsoft.AspNetCore.Mvc;
+using Shogi.Api.Controllers;
+using Shogi.Api.Extensions;
+using Shogi.Api.Identity;
+using Shogi.Api.Repositories;
+using Shogi.Api.Repositories.Dto;
+using Shogi.Contracts.Api;
+using Shogi.Domain.Aggregates;
+using System.Data.SqlClient;
+
+namespace Shogi.Api.Application;
+
+public class ShogiApplication(
+	QueryRepository queryRepository,
+	SessionRepository sessionRepository,
+	UserManager<ShogiUser> userManager,
+	GameHubContext gameHubContext)
+{
+
+	public async Task<IActionResult> CreateSession(string playerId)
+	{
+		var session = new Session(Guid.NewGuid(), playerId);
+
+		try
+		{
+			await sessionRepository.CreateSession(session);
+			return new CreatedAtActionResult(
+				nameof(SessionsController.GetSession),
+				null,
+				new { sessionId = session.Id.ToString() },
+				session.Id.ToString());
+		}
+		catch (SqlException)
+		{
+			return new ConflictResult();
+		}
+	}
+
+	public async Task<IEnumerable<SessionDto>> ReadAllSessionMetadatas(string playerId)
+	{
+		return await queryRepository.ReadSessionsMetadata(playerId);
+	}
+
+	public async Task<Session?> ReadSession(string id)
+	{
+		var (sessionDto, moveDtos) = await sessionRepository.ReadSessionAndMoves(id);
+		if (!sessionDto.HasValue)
+		{
+			return null;
+		}
+
+		var session = new Session(Guid.Parse(sessionDto.Value.Id), sessionDto.Value.Player1Id);
+		if (!string.IsNullOrWhiteSpace(sessionDto.Value.Player2Id)) session.AddPlayer2(sessionDto.Value.Player2Id);
+
+		foreach (var move in moveDtos)
+		{
+			if (move.PieceFromHand.HasValue)
+			{
+				session.Board.Move(move.PieceFromHand.Value, move.To);
+			}
+			else if (move.From != null)
+			{
+				session.Board.Move(move.From, move.To, false);
+			}
+			else
+			{
+				throw new InvalidOperationException($"Corrupt data during {nameof(ReadSession)}");
+			}
+		}
+
+
+
+		return session;
+	}
+
+	public async Task<IActionResult> MovePiece(string playerId, string sessionId, MovePieceCommand command)
+	{
+		var session = await this.ReadSession(sessionId);
+		if (session == null)
+		{
+			return new NotFoundResult();
+		}
+
+		if (!session.IsSeated(playerId))
+		{
+			return new ForbidResult();
+		}
+
+		try
+		{
+			if (command.PieceFromHand.HasValue)
+			{
+				session.Board.Move(command.PieceFromHand.Value.ToDomain(), command.To);
+			}
+			else
+			{
+				session.Board.Move(command.From!, command.To, command.IsPromotion ?? false);
+			}
+		}
+		catch (InvalidOperationException e)
+		{
+			return new ConflictObjectResult(e.Message);
+		}
+
+		await sessionRepository.CreateMove(sessionId, command);
+
+		await gameHubContext.Emit_PieceMoved(sessionId);
+
+		return new NoContentResult();
+
+	}
+
+	public async Task<IActionResult> JoinSession(string sessionId, string player2Id)
+	{
+		var session = await this.ReadSession(sessionId);
+		if (session == null) return new NotFoundResult();
+
+		if (string.IsNullOrEmpty(session.Player2))
+		{
+			session.AddPlayer2(player2Id);
+
+			await sessionRepository.SetPlayer2(sessionId, player2Id);
+
+			var player2Email = this.GetUsername(player2Id);
+			await gameHubContext.Emit_SessionJoined(sessionId);
+
+			return new OkResult();
+		}
+
+		return new ConflictObjectResult("This game already has two players.");
+	}
+
+	public string GetUsername(string? userId)
+	{
+		if (string.IsNullOrEmpty(userId))
+		{
+			return string.Empty;
+		}
+
+		return userManager.Users.FirstOrDefault(u => u.Id == userId)?.UserName!;
+	}
+}