Converts LocalDate and Instant from java.time to/from Play JSON for MongoDB use

JsonImplicits.scala

import java.time.{Instant, LocalDate, ZoneOffset}

import play.api.libs.json._

object JsonImplicits {

  implicit object LocalDateMongoJsonReaderWriter extends Reads[LocalDate] with Writes[LocalDate] {
    override def reads(json: JsValue): JsResult[LocalDate] =
      (json \ "$date").validate[Long].map(Instant.ofEpochMilli(_).atZone(ZoneOffset.UTC).toLocalDate)

    override def writes(date: LocalDate): JsValue =
      Json.obj("$date" -> date.atStartOfDay().atZone(ZoneOffset.UTC).toInstant.toEpochMilli)
  }

  implicit object InstantMongoJsonReaderWriter extends Reads[Instant] with Writes[Instant] {
    override def reads(json: JsValue): JsResult[Instant] =
      (json \ "$date").validate[Long].map(Instant.ofEpochMilli)

    override def writes(instant: Instant): JsValue =
      Json.obj("$date" -> instant.toEpochMilli)
  }

}