Attribute grade overrides from proctoring to the final reviewer

More generally, makes it so we don't ever pull in the user to whom
we're attributing overrides from the request, but always use the one
passed in via method parameters

Also pass through comments, if they're provided via this method

JIRA:EDUCATOR-4641

lms/djangoapps/grades/rest_api/v1/tests/test_gradebook_views.py

@@ -1813,6 +1813,27 @@ class SubsectionGradeViewTest(GradebookViewTestBase):
 
         assert expected_data == resp.data
 
+    def test_comment_appears(self):
+        """
+        Test that comments passed (e.g. from proctoring) appear in the history rows
+        """
+        proctoring_failure_fake_comment = "Failed Test Proctoring"
+        self.login_course_staff()
+        override = PersistentSubsectionGradeOverride.update_or_create_override(
+            requesting_user=self.global_staff,
+            subsection_grade_model=self.grade,
+            earned_all_override=0.0,
+            earned_graded_override=0.0,
+            feature=GradeOverrideFeatureEnum.proctoring,
+            comment=proctoring_failure_fake_comment
+        )
+
+        resp = self.client.get(
+            self.get_url(subsection_id=self.usage_key)
+        )
+
+        assert resp.data['history'][0]['override_reason'] == proctoring_failure_fake_comment
+
     @ddt.data(
         'login_staff',
     )