I have a need to build secure pages on a website by integrating with an external identity system. The external IDP has its own login page and it will redirect to AEM secure page after successful login after setting an identity cookie. I want to use this external login to establish authenticated session in AEM so that I can use AEM ACLs and permission handling. However, I do not want to sync users in AEM and may be just use a single pre-created user(with right group mappings) to login in AEM.I will validate the cookie with external IDP before I create a session in AEM with pre-created user. How can I achieve this ?