Return content type gate for staff users when masquerading as the Learner in Audit or Learner in Limited Access Roles

This is necessary to display the content type gate in the UI
AA-613

openedx/core/djangoapps/courseware_api/views.py

@@ -479,6 +479,13 @@ class SequenceMetadata(DeveloperErrorViewMixin, APIView):
         except InvalidKeyError:
             raise NotFound("Invalid usage key: '{}'.".format(usage_key_string))
 
+        _, request.user = setup_masquerade(
+            request,
+            usage_key.course_key,
+            staff_access=has_access(request.user, 'staff', usage_key.course_key),
+            reset_masquerade_data=True,
+        )
+
         sequence, _ = get_module_by_usage_id(
             self.request,
             str(usage_key.course_key),