Circe support - @noflat has no effect when KebsCirce.NoFlat is not used

[pk044]

  object KebsProtocol extends KebsCirce
  import KebsProtocol._

  @noflat case class F(i: Int)

  test("No-flat format - annotation") {

    val decoder = implicitly[Decoder[F]]
    val encoder = implicitly[Encoder[F]]
    decoder.apply(Json.fromFields(Seq("i" -> Json.fromInt(10))).hcursor) shouldBe Right(F(10))
    encoder.apply(F(10)) shouldBe Json.fromFields(Seq("i" -> Json.fromInt(10)))
  }

Test above results in failure. Currently the support for noflat works only when NoFlat trait is mixed in.

In order to fix this, the following code should be changed so @noflat is taken into account when only KebsCirce trait is extended:

trait KebsCirce extends AutoDerivation {
  implicit def flatDecoder[T, A](implicit rep: CaseClass1Rep[T, A], decoder: Decoder[A]): Decoder[T] =
    decoder.emap(obj => Try(rep.apply(obj)).toEither.left.map(_.getMessage))
  implicit def flatEncoder[T, A](implicit rep: CaseClass1Rep[T, A], encoder: Encoder[A]): Encoder[T] =
    encoder.contramap(rep.unapply)
}

KebsSpray is already handling this - it's worth taking a look: https://github.com/theiterators/kebs/blob/bb83e41ec2e3a217719c2da083e99e8ca4eee0ba/spray-json/src/main/scala/pl/iterators/kebs/json/KebsSpray.scala