auto-autheticate a user when logged in via custom login

I am using Azure AD (Active Directory) to login and I am also using custom AUTH_USER_MODEL (application_user).

@ms_identity_web.login_required

I have imported all user data from Azure AD to the application_user table. (I will take care of new users)

Now the login is working when someone logs in using their business365 / office365 credentials. But since this is not recognized as a Django user login, I would need to replicate the whole lot of django app functionality, esp DRF.

Instead, I want to auto-login / auto-authenticate the default Django login when someone logs in using their business365 credentials.

How do I auto-authenticate ?