Fix the inclusion of relations

When getting a list and including data from the models in the list, only
the related data of the first model in the list was included

Author: schtibe

rest_framework_json_api/utils.py

@@ -413,14 +413,13 @@ def extract_included(fields, resource, resource_instance, included_resources):
         if not isinstance(field, (RelatedField, ManyRelatedField, BaseSerializer)):
             continue
 
-        try:
-            included_resources.remove(field_name)
-            new_included_resources = [key.replace('%s.' % field_name, '', 1) for key in included_resources]
-            relation_instance_or_manager = getattr(resource_instance, field_name)
-            serializer_data = resource.get(field_name)
-        except ValueError:
+        if field_name not in included_resources:
             # Skip fields not in requested included resources
             continue
+        
+        new_included_resources = [key.replace('%s.' % field_name, '', 1) for key in included_resources]
+        relation_instance_or_manager = getattr(resource_instance, field_name)
+        serializer_data = resource.get(field_name)
 
         if isinstance(field, ManyRelatedField):
             serializer_class = included_serializers.get(field_name)