Finds all of the course offerings in a course set that are current for any given
academic session (regardless of the courseOffering's start and end dates).
Finds all Sections that are linked to an EnrollmentSet for which a user is an
instructor of record and which are part of a CourseOffering in a given
AcademicSession.
Constructs an IdNotFoundException with a generic message (useful when the
more specific constructor isn't suitable, because we don't know what kind of ID
wasn't found).