WithId

sealed abstract class InternalIdentifiable {
  self =>
  type Identifier
  def withId(identifier: Identifier): WithId[self.type] =
    WithId[self.type](identifier, self)
}

abstract class Identifiable[Identifier0] extends InternalIdentifiable {
  type Identifier = Identifier0
}

final case class WithId[A <: InternalIdentifiable](id: A#Identifier, model: A)

object Usage {
  final case class MyModelId(id: String) extends AnyVal
  final case class MyModel(payload: Int) extends Identifiable[MyModelId]

  val myModel: MyModel = MyModel(42)
  val idOfSavedModel: MyModelId = saveNewToDB(myModel)
  val retrievedModelWithId: WithId[MyModel] = retrieveFromDB(idOfSavedModel)

  def saveNewToDB(model: MyModel): MyModelId = MyModelId("idString")
  def retrieveFromDB(id: MyModelId): WithId[MyModel] = MyModel(42).withId(id)
}