I'm attempting to develop a website that would require users to have separate access to information with one manager (or administrator) for their group. For example, the site may include 5 different groups. Each group has 10 members. One of those members has admin authority over that group only. That person can invite additional users and add/change content for his group only. I'd like as much of this as possible to be automated (signup and group assignment). Is there a Content Management System that is best for this?