HTTP.Context System Variables inside Container

I’m migrating two legacy applications to docker container to execute in ECS. I have the applications in containers and successfully executing. The issue I’m working through now is that both rely on the value of Request.ServerVariables(“REMOTE_USER”) to determine if the current user has access to the application.

When executing inside the container this value is returned as empty string or null. I've tried a few different variables, methods to obtain this value to no avail.

Is there a method to making this value available within the container? I’ve searched online and have come up empty.