Add Annotation to treat Either like some sort of "Union"

[BalduinLandolt]

Maybe I'm missing something and there is already a (much better) way to do this...
But when using Either, the JSON serialization does not do what I was hoping for:

The following simple script

import zio._
import zio.json._

final case class Something(
    value: Either[String, Int]
)
object Something {
  implicit val codec: JsonCodec[Something] = DeriveJsonCodec.gen[Something]
}

object MyApp extends ZIOAppDefault {
  def run = for {
    _ <- ZIO.unit
    s  = Something(Left("foo"))
    _ <- Console.printLine(s.toJson)
    i  = Something(Right(42))
    _ <- Console.printLine(i.toJson)
  } yield ()
}

prints:

{"value":{"Left":"foo"}}
{"value":{"Right":42}}

Whereas I was actually hoping to get something more like

{"value":"foo"}
{"value":42}

Of course the same goes for decoding.

If there is already a good way to achieve this, I'd be happy to know.
If not, I've been thinking that it could be an option to have an annotation to get this behaviour if wanted. Something along the lines of:

final case class Something(
    @jsonEitherAsUnion(true)
    value: Either[String, Int]
)
object Something {
  implicit val codec: JsonCodec[Something] = DeriveJsonCodec.gen[Something]
}

(I'm sure one could come up with a smarter name for it...)

What do you guys think? And if so, could that be something for the hackathon?

[hardlianotion]

(Many months after the fact ...)

Could you use the mapping functionality to get what you want as a manual step in either direction?