The forced authentication makes users log in with IdP credentials only and no longer allows them to log in with Drupal credentials. The module provides the following options for this functionality:
1. Auto redirect the user to IdP: Every time a user tries to access the Drupal login page, they'll be redirected to the IdP login page.
2. Protect website against anonymous access: If a user tries to access any page of the Drupal site, they'll be redirected to the IdP login page.
How to enable this feature?
Navigate to the Signin tab of the module
Enable the checkbox, Auto redirect the user to IdP or Protect website against anonymous access as per your requirement.
How to access the site using Drupal credentials if something goes wrong on the IdP side?
The backdoor URL allows admin users to log in using the Drupal credentials even if forced authentication is turned on.
Navigate to Signin tab of the module.
Check the option - Enable backdoor login.
Note down the backdoor URL. Use this URL in case you are unable to log in using the IDP.