Play JSON Option[String] deserializer

OptionalStringReads.scala

  implicit object OptionalStringReads extends Reads[Option[String]] {
    def reads(json: JsValue) = json match {
      case JsString(s) => JsSuccess(Some(s))
      case JsNull      => JsSuccess(None)
      case _           => JsError("error.expected.jsstring")
    }
  }