Add option to specify default included resources

Let's provide an extra JSONAPIMeta configuration option that specifies
resources to be listed in the 'included' section of the response.
These resources shall be included even if they're not explicitly mentioned
in the 'include' request parameter.

Author: knaperek

rest_framework_json_api/renderers.py

@@ -415,12 +415,6 @@ def render(self, data, accepted_media_type=None, renderer_context=None):
         if resource_name == 'errors':
             return self.render_errors(data, accepted_media_type, renderer_context)
 
-        include_resources_param = request.query_params.get('include') if request else None
-        if include_resources_param:
-            included_resources = include_resources_param.split(',')
-        else:
-            included_resources = list()
-
         json_api_data = data
         json_api_included = list()
         # initialize json_api_meta with pagination meta or an empty dict
@@ -433,6 +427,13 @@ def render(self, data, accepted_media_type=None, renderer_context=None):
 
         serializer = getattr(serializer_data, 'serializer', None)
 
+        # Build a list of included resources
+        included_resources = utils.get_default_included_resources_from_serializer(serializer)
+        include_resources_param = request.query_params.get('include') if request else None
+        if include_resources_param:
+            extra = filter(lambda r: r not in included_resources, include_resources_param.split(','))
+            included_resources.extend(extra)
+
         if serializer is not None:
 
             # Get the serializer fields

rest_framework_json_api/utils.py

@@ -232,6 +232,13 @@ def get_resource_type_from_serializer(serializer):
         return get_resource_type_from_model(serializer.Meta.model)
 
 
+def get_default_included_resources_from_serializer(serializer):
+    try:
+        return list(serializer.JSONAPIMeta.included_resources)
+    except AttributeError:
+        return []
+
+
 def get_included_serializers(serializer):
     included_serializers = copy.copy(getattr(serializer, 'included_serializers', dict()))