Automatically add interfaces when deriving ObjectTypes

[danestig]

Would it be possible to let the derive macros automatically add interfaces to objects? In the below example the Foo class extends the trait Bar and there exists an InterfaceType for type Bar. I think the macro should add the interface to the type.

trait Bar
  case class Foo(foo: String) extends Bar

  implicit lazy val BarInterfaceType: InterfaceType[_, Bar] =
    InterfaceType(
      name = "Bar",
      fields = sangria.schema.fields()
    )

  implicit lazy val FooObjectType = deriveObjectType[_, Foo](
    Interfaces(BarInterfaceType)  // Can this part be removed?
  )

I