PUT endpoint does not return correct id (maybe rowid?)

Bug or feature request

• [X ] Bug
• Feature request

Description of feature (or steps to reproduce if bug)

Create a model with an id as type "string", and a defaultFN of "uuid". PUT a new instance using the REST api through explorer. The response body will show an integer id (presumably an integer that corresponds to the ROWID or something like that). Now use the GET api to list all model instances. The instance will show an id in the correct uuid format.

Link to sample repo to reproduce issue (if bug)

Expected result

I'm assuming the response body should reflect the id generated by defaultFN.

Actual result (if bug)

Its an integer.

Additional information (Node.js version, LoopBack version, etc)

Loopback 3, node 8.11.2

I'm anticipating a reply of "why are you using a string for a key?" The answer is complicated based in integration with a larger project. If the answer is "we don't support that" we'll make it work, but I wanted to check to make sure. Thanks

Reproduce el caso de LoopBack 3 creando un modelo con un id de tipo string y uuid defaultFN; después, envía una nueva instancia mediante PUT a través del REST API Explorer. Compara la respuesta de PUT con el id devuelto al listar instancias mediante GET; se considera terminado cuando la respuesta de PUT devuelve el UUID generado en lugar de un entero.