Refactor data layer, add business layer

DataLayer/scripts/crud/USP_CreateUserAccount.sql

@@ -0,0 +1,36 @@
+
+CREATE OR ALTER PROCEDURE usp_CreateUserAccount
+(
+    @UserAccountId UNIQUEIDENTIFIER = NULL,
+    @Username VARCHAR(64),
+    @FirstName NVARCHAR(128),
+    @LastName NVARCHAR(128),
+    @DateOfBirth DATETIME,
+    @Email VARCHAR(128)
+)
+AS
+BEGIN
+    SET NOCOUNT ON
+    SET XACT_ABORT ON
+    BEGIN TRANSACTION
+
+    INSERT INTO UserAccount 
+    (
+        UserAccountID,
+        Username,
+        FirstName,
+        LastName,
+        DateOfBirth,
+        Email
+    )
+    VALUES
+    (
+        COALESCE(@UserAccountId, NEWID()),
+        @Username,
+        @FirstName,
+        @LastName,
+        @DateOfBirth,
+        @Email
+    );
+    COMMIT TRANSACTION
+END;