Create/check grading opportunities in database on validate, not start

[inducer]

cc @lukeolson

[lukeolson]

In addition, on a "fetch and update", a "Course content validated successfully" appears. It would be handy to see 1) what was validated, 2) if any grading opportunities were created, and 3) anything else that happened on validation. I'm picturing an expandable list but there may be other ways.