squash a bunch of commits

Shogi.Database/Session/Tables/BoardState.sql

@@ -0,0 +1,10 @@
+CREATE TABLE [session].[BoardState]
+(
+	[Id] BIGINT NOT NULL PRIMARY KEY IDENTITY,
+	[Document] NVARCHAR(max) NOT NULL,
+	[SessionId] BIGINT NOT NULL,
+
+	CONSTRAINT [Document must be json] CHECK (isjson(Document)=1),
+	CONSTRAINT FK_BoardState_Session FOREIGN KEY (SessionId) 
+		REFERENCES [session].[Session] (Id) ON DELETE CASCADE ON UPDATE CASCADE
+)