Introducing Login view.

This will affect /v2/actions/login URL
The @auth_required decorator is where the authentication happens. I was just working in there and it requires the user to either be authentication with http or provide a username and password as headers.

It's also correct that we are not using the Django auth system yet. If we were then we wouldn't need the @auth_required decorator at the top and the Django middleware would reject an unauthorized request before the code ever gets here. Eventually that is what we're going to be doing.