Added methods to GradingRecord Logic to facilitate creating/updating them.
UpdateOrCreateRecordsFor will batch put GradingRecords for a given SurveyGroup and StudentProject.
getFieldsForGradingRecord will return the fields that need to be set for a single GradingRecord entity given a StudentProject, GradingSurveyGroup and if it is an update a GradingRecord entity.
"""
>>> from django.contrib.sites.models import Site
>>> from django.conf import settings
>>> Site(id=settings.SITE_ID, domain="example.com", name="example.com").save()
>>> # Make sure that get_current() does not return a deleted Site object.
>>> s = Site.objects.get_current()
>>> isinstance(s, Site)
True
>>> s.delete()
>>> Site.objects.get_current()
Traceback (most recent call last):
...
DoesNotExist: Site matching query does not exist.
"""