Foreman » Installer

I revised the Pulp docs here based on some of my testing: https://github.com/pulp/pulpcore/pull/2399/files

To recap the convo where we determined we don't think katello needs a change:
1. katello creates the 'admin' user in its installer (this is a django user in pulp's DB created with pulpcore-manager ...)
2. The external auth configured today is expected to receive the 'admin' user from the DB
3. Because the user exists in the DB, and that user is an admin, the default permission_classes of Pulp should continue to allow everything to work since admins pass all permissions checks.