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.Database/Session/Functions/MaxNewSessionsPerUser.sql

@@ -0,0 +1,18 @@
+CREATE FUNCTION [session].[MaxNewSessionsPerUser]() RETURNS INT
+AS
+BEGIN
+	
+	DECLARE @MaxNewSessionsCreatedByAnyOneUser INT;
+
+	WITH CountOfNewSessionsPerPlayer AS
+	(
+	SELECT COUNT(*) as TotalNewSessions
+		FROM [session].[Session]
+		WHERE Player2Id IS NULL
+		GROUP BY Player1Id
+	)
+	SELECT @MaxNewSessionsCreatedByAnyOneUser = MAX(CountOfNewSessionsPerPlayer.TotalNewSessions)
+	FROM CountOfNewSessionsPerPlayer
+
+	RETURN @MaxNewSessionsCreatedByAnyOneUser
+END