public async Task <ActionResult> Login(string userName = "", string currentTenancyName = "", string returnUrl = "")
        {
            if (string.IsNullOrWhiteSpace(returnUrl))
            {
                returnUrl = Url.Action("Index", "Home");
            }
            var allTenants = await _tenantManager.All();

            return(View(new LoginFormViewModel
            {
                UserName = userName,
                ReturnUrl = returnUrl,
                Tenants = allTenants,
                CurrentTenancyName = currentTenancyName
            }));
        }