Introduce mapped-superclass

[aledeg]

I think it could be really nice to change entities to mapped superclass to be able to inherit those class when needed. A little bit like FOSUserBundle does.

At the moment, I would like to add informations in the Client and the User entities but as a limitation with Doctrine and Entities, I can't do that without changing the server code. But I guess, it could be useful also with other entities.

[Jeroenkeesom]

👍