Pick a value for line_item_url in all contexts

The grading service might operate in two different contexts:

- While on a launch

Here take the value directly from LTIParams

- On an API call from the front end

Here we will forward the value to the frontend which will send it back
in `parsed_params`

lms/services/lti_grading/factory.py

@@ -8,7 +8,10 @@ def service_factory(_context, request):
 
     if application_instance.lti_version == "1.3.0":
         return LTI13GradingService(
-            line_item_url=request.parsed_params.get("lis_outcome_service_url"),
+            # Pick the value from the right dictionary depending on the context we are running
+            # either an API call from the frontend (parsed_params) or inside an LTI launch (lti_params).
+            line_item_url=request.parsed_params.get("lis_outcome_service_url")
+            or request.lti_params.get("lis_outcome_service_url"),
             line_item_container_url=request.lti_params.get("lineitems"),
             ltia_service=request.find_service(LTIAHTTPService),
         )

tests/unit/lms/services/lti_grading/factory_test.py

@@ -28,12 +28,28 @@ def test_v13(self, pyramid_request, LTI13GradingService, ltia_http_service):
         )
         assert svc == LTI13GradingService.return_value
 
+    def test_v13_line_item_url_from_lti_params(
+        self, pyramid_request, LTI13GradingService, ltia_http_service
+    ):
+        del pyramid_request.parsed_params["lis_outcome_service_url"]
+        pyramid_request.lti_user.application_instance = Mock(lti_version="1.3.0")
+
+        svc = service_factory(sentinel.context, pyramid_request)
+
+        LTI13GradingService.assert_called_once_with(
+            sentinel.grading_url, sentinel.lineitems, ltia_http_service
+        )
+        assert svc == LTI13GradingService.return_value
+
     @pytest.fixture
     def pyramid_request(self, pyramid_request):
         pyramid_request.parsed_params = {
             "lis_outcome_service_url": sentinel.grading_url
         }
-        pyramid_request.lti_params = {"lineitems": sentinel.lineitems}
+        pyramid_request.lti_params = {
+            "lineitems": sentinel.lineitems,
+            "lis_outcome_service_url": sentinel.grading_url,
+        }
 
         return pyramid_request