[Serializer] Name Converter

| Q                | A
| --------------- | ---
| Doc fix?      | no
| New docs? | yes symfony/symfony#13120
| Applies to   | 2.7

This is the documentation for the Serializer Name Converter feature.
It's to make `properties or getters` a possesion of the PHP class. However, if I'm correct you should use `'s` for a single owner (one PHP class) and just `'` for multiple owners (PHP classes' properties or getter).

Even more, since both objects are things and not humans, I think using `... of ...` is better: "different than properties, getter or setter methods of the PHP class"