api/swid-stats: new tag__product_name and tag_version filters

The TagStats serializer now includes a TagMiniSerializer
displaying the package_name, version and unique_id tag fields.
tag__package_name, tag__version and tag__unique_id can be used in
the TagStatsView (api/swid-stats)  as filter parameters.

apps/swid/api_views.py

@@ -35,7 +35,8 @@ class TagViewSet(viewsets.ReadOnlyModelViewSet):
 class TagStatsViewSet(viewsets.ReadOnlyModelViewSet):
     model = TagStats
     serializer_class = serializers.TagStatsSerializer
-    filter_fields = ('tag', 'device', 'first_seen', 'last_seen')
+    filter_fields = ('tag', 'tag__package_name', 'tag__version', 'tag__unique_id',
+                     'device', 'first_seen', 'last_seen')
 
 
 def validate_data_param(request, list_name):

apps/swid/serializers.py

@@ -42,7 +42,15 @@ class Meta(object):
                   'entities', 'events', 'swid_xml')
 
 
+class TagMiniSerializer(DynamicFieldsMixin, serializers.HyperlinkedModelSerializer):
+
+    class Meta(object):
+        model = models.Tag
+        fields = ('id', 'uri', 'package_name', 'version', 'unique_id')
+
+
 class TagStatsSerializer(DynamicFieldsMixin, serializers.HyperlinkedModelSerializer):
+    tag = TagMiniSerializer()
 
     class Meta(object):
         model = models.TagStats