Anonymous swagger definitions generate subpar code

Hello!

Following swagger code:

```yaml
swagger: '2.0'
paths:
/dummy:
post:
operationId: dummy
responses:
200:
schema:
type: object
properties:
foo:
type: string
bar:
type: string
```

generate this code:

```scala
sealed abstract class DummyResponse {
def fold[A](handleOk: io.circe.Json => A): A = this match {
case x: DummyResponse.Ok =>
handleOk(x.value)
}
}
object DummyResponse { case class Ok(value: io.circe.Json) extends DummyResponse }
```

I think we can do better - thoughts? I will try to tackle this myself, just want to check if there is a good reason for the code above to be generated in such a shape, without strict definition