add discovery=true filter to discovery editoral endpoint

docs/topics/api/discovery.rst

@@ -54,10 +54,12 @@ Editorial Content
 
 This endpoint allows you to fetch all editorial content for Discovery Pane
 Recommendations. This is used internally to generate .po files containing the
-strings the content team came up with.
+strings defined by the content team.  It is also used by TAAR service to obtain a list
+of appropriate add-ons to recommended.
 
  .. http:get:: /api/v4/discovery/editorial/
 
+    :query boolean recommended: Filter to only add-ons recommended by Mozilla.  Only ``recommended=true`` is supported.
     :>json array results: The array containing the results for this query. There is no pagination, all results are returned.
     :>json object results[].addon: A :ref:`add-on <addon-detail-object>` object for this item, but only containing one field: ``guid``.
     :>json string|null results[].custom_heading: The custom heading for this item, if any.

src/olympia/discovery/tests/test_views.py

@@ -379,3 +379,24 @@ class TestDiscoveryItemViewSet(TestCase):
         assert result['custom_description'] == (
             u'This time with a custom description')
         assert result['addon'] == {'guid': self.items[2].addon.guid}
+
+    def test_recommended(self):
+        with self.assertNumQueries(1):
+            response = self.client.get(self.url + '?recommended=true')
+        assert response.status_code == 200
+        assert len(response.data['results']) == 0
+
+        self.items[0].update(recommendable=True)
+        self.items[0].addon.current_version.update(
+            recommendation_approved=True)
+        self.items[2].update(recommendable=True)
+        self.items[2].addon.current_version.update(
+            recommendation_approved=True)
+        with self.assertNumQueries(1):
+            response = self.client.get(self.url + '?recommended=true')
+        assert response.status_code == 200
+        assert len(response.data['results']) == 2
+        assert response.data['results'][0]['addon']['guid'] == (
+            self.items[0].addon.guid)
+        assert response.data['results'][1]['addon']['guid'] == (
+            self.items[2].addon.guid)

src/olympia/discovery/views.py

@@ -87,6 +87,14 @@ class DiscoveryItemViewSet(ListModelMixin, GenericViewSet):
         'addon').order_by('pk')
     serializer_class = DiscoveryEditorialContentSerializer
 
+    def filter_queryset(self, qs):
+        qs = super().filter_queryset(qs)
+        if self.request.query_params.get('recommended', False) == 'true':
+            qs = qs.filter(**{
+                'recommendable': True,
+                'addon___current_version__recommendation_approved': True})
+        return qs
+
     def list(self, request, *args, **kwargs):
         # Ignore pagination (fetch all items!) but do wrap the data in a
         # `results` property to mimic what the rest of our APIs do.