Major Description
It's not possible to perform multiple ratings with several users when using Ratings with separate pages and separate spaces.
Reproduction steps:
1. Install ratings and configure it to use separate page and space: 
2. Rate a page with an user
3. Login with another user and try to rate the same page
Expected result:
- Two ratings are saved
Obtained result:
- It's not possible to save the second rating and the following alert box is shown:
