FilterableField option to exclude from ObjectType

[mwoelk]

Is your feature request related to a problem? Please describe.
It would be great if there's an filterOnly option in the arguments of @FilterableField so that this field would only appear as filter but not as field in the generated ObjectType.

Why is this good to have? E.g. when working with federation we might want to filter using the id of a federated relation.
But we only want to have the relation itself in the resulting object type.

Have you read the Contributing Guidelines?

yes

Describe the solution you'd like

@FilterableField({filterOnly: true})
federatedRelationId: string;

Describe alternatives you've considered
Just leaving the id field in which unnecessarily bloats up the API.