lowerCamelCase for getter and setter method names

getter and setter methods of models should be lowerCamelCased from now
on. underscored_naming is still supported but deprecated.

That means you should for example rename the method get_user_id to
getUserId.

As a bonus you get special twig support. You can use {{ item.userId }}
instead of {{ item.get_user_id }} to access the getter.