only redirect to dashboard if user has course enrollments, otherwise rem...

...ain on the course catalog page (aka homepage or root)

We got some UX feedback on our white label sites where it is a poor experience for logged in users to be redirected to their dashboard when they have no enrolled courses. It is felt that it is confusing to the end-user what he/she should do after that redirect.
I think I would slightly prefer it if the `not microsite_org` case was pulled out of the list comprehension into an explicit case of its own.  But this doesn't block the review.