Hi ShiXuan Teng,
You need to configure it in the Users app. For NTLM (and Kerberos), if I'm not mistaken you would use the Active Directory option with Windows Integrated Authentication enabled (and no need for any integrated login page, as the Windows credentials would be automatically used).
This being said, NTLM authentication doesn't seem to be supported for Reactive Apps (as per the first link on this post). Alternatively, you can use Azure AD or SAML 2.0 authentication alternatives and enable the Single Sign-On Between App Types (they require a bit more configuration).
Once that is done, it naturally integrates with the OutSystems User entity, so the system action GetUserId()
will return the logged-in user's Id. All user information would be accessible by querying the database GetUser(GetUserId())
would get you the User record of the currently logged-in user.
Hope this helps!