public async Task <IActionResult> OnGetLinkLoginCallbackAsync()
        {
            var user = await _userManager.GetUserAsync(User);

            if (user == null)
            {
                return(NotFound($"Unable to load user with ID '{_userManager.GetUserId(User)}'."));
            }

            var info = await _signInManager.GetExternalLoginInfoAsync(await _userManager.GetUserIdAsync(user));

            if (info == null)
            {
                throw new InvalidOperationException($"Unexpected error occurred loading external login info for user with ID '{user.Id}'.");
            }

            var logins = await _userManager.GetLoginsAsync(user);

            if (logins.Any(l => l.LoginProvider == info.LoginProvider && l.ProviderKey == info.ProviderKey))
            {
                StatusMessage = "The external login is already linked to your account.";
                return(RedirectToPage());
            }

            var email  = info.Principal.Claims.FindEmail();
            var result = await _userManager.AddLoginAsync(user, info, email);

            if (!result.Succeeded)
            {
                throw new InvalidOperationException($"Unexpected error occurred adding external login for user with ID '{user.Id}'.");
            }

            // Clear the existing external cookie to ensure a clean login process
            await HttpContext.SignOutAsync(IdentityConstants.ExternalScheme);

            StatusMessage = "The external login was added.";
            return(RedirectToPage());
        }