text: Title: Retrieve object primary keys with Relay
  Body: Hello,
  Using Relay, the `id` field is not the primary key of the ingredients objects in the database. Is there a way to get it back ?
  
  ```
  query {
    allIngredients {
      edges {
        node {
          id,
          name
        }
      }
    }
  }
  ```
  
  Thanks,