Add a new waffle switch that allows us to assume zero grades for
learners who have no entry previously recorded, and another to
disable persisting grades for unengaged learners.
TNL-6691
Remove deprecated SingleSectionGrader. TNL-5987
Remove display_name and module_id from Scores objects
Update CourseGradeFactory.__init__ to not be user-specific
Update some callers to use CourseGrade class instead of "summary" dict
Remove no longer needed course_grades.py module.
Renamed django signal from GRADES_UPDATED to COURSE_GRADE_CHANGED
Two new certificate statuses are introduced, 'audit_passing' and
'audit_notpassing'. These signal that the GeneratedCertificate is not
to be displayed as a cert to the user, and that they either passed or
did not. This allows us to retain existing grading logic, as well as
maintaining correctness in analytics and reporting.
Ineligible certificates are hidden by using the
`eligible_certificates` manager on GeneratedCertificate. Some places
in the coe (largely reporting, analytics, and management commands) use
the default `objects` manager, since they need access to all
certificates.
ECOM-3040
ECOM-3515
