Authentication includes access to main site on multisite install

[leslieg]

Using Shibboleth on multisite install - new authenticated users are automatically added to the main site with whatever user role is mapped or set as default. In our installation, users are not supposed to have access to the main site, they are authenticating so that they can make new websites. I can set them to view only but it's confusing for them that they have this other site listed. I'd love to see the ability to authenticate and not auto add them to any site - in the same way that I can manually add users without associating them with a particular site.