Feature request: Have an option to automatically populate

[BorntraegerMarc]

It would be awesome if one could not only specify to check whether the ObjectId reference exists but if it does it would also immediately populate the document!

As this library already makes a query to the DB I thought it might be the right place to introduce an option to populate the query result to the response.

At the moment I need to use this validator + another populate from mongoose. So in total 2 queries are executed, which could have been handled with 1.

I wanted to ask whether you would be interested in such a feature and if yes I could provide a PR

[Alutun]

I'm exactly in the same case, I'm not sure if it should not be the other way around of an option of the populate method. But we can always start from this way.