[API-66] Decouple serializers

https://github.com/GoIntegro/hateoas-bundle/issues/51
https://github.com/GoIntegro/hateoas-bundle/issues/53
https://github.com/GoIntegro/hateoas-bundle/issues/54
https://github.com/GoIntegro/hateoas-bundle/issues/55
https://github.com/GoIntegro/hateoas-bundle/issues/56