public async Task <IActionResult> Register([FromBody] RegistrationRequest user)
        {
            var passwordValidationRes = AuthenticationHelper.CheckPasswordRequierments(user.Password);

            if (passwordValidationRes != null)
            {
                return(BadRequest(passwordValidationRes));
            }

            if (await _usersService.IsUserExists(user.UserName))
            {
                return(UnprocessableEntity($"user name {user.UserName} is taken"));
            }

            await _usersService.Register(user);

            var redirectUrl = _urlHelper.Link("Login", null);

            return(Redirect(redirectUrl));
        }