Make `_id: false` disable `id` virtual as well

To disable the generation of an _id for a schema, I’m using

_id: false,
firstName: String,
lastName: String,

When inspecting a document of this schema, one gets

> console.log(doc);
  Object { firstName: 'karl', lastName: 'hungus' }

But

> console.log(doc._id);
  null

and

> console.log(doc.toJSON({virtuals: true}));
  Object { id: null, firstName: 'karl', lastName: 'hungus' }

Apparently, _id has somehow been transformed into a virtual field.

This makes it impossible to an actual virtual field (e.g., fullName), have it transformed to JSON and not include id.

[vkarpov15]

Fixed but in hindsight I want to undo the refactor I did to move idGetter from being a plugin to being a helper. It’s better off as a plugin because you may do something like const schema = new Schema({}, { _id: false }); schema.add({ _id: Number });. If idGetter isn’t a plugin, it won’t get added in the latter case.

[vkarpov15]

@adamreisnz that’s a fair point, we’ll change that for our next major release