Custom sub-project Messages overriding example

I18nComponents.scala

trait I18nComponents {

  def environment: Environment
  def configuration: Configuration
  
  // NOTE line 10! Load subproject messages, and override with available root project messages.
  lazy val messagesApi: MessagesApi = new DefaultMessagesApi(environment, configuration, langs) {
    override protected def loadAllMessages: Map[String, Map[String, String]] = {
      langs.availables.map(_.code).map { lang =>
        (lang, loadMessages("messages.mysubproject." + lang) ++ loadMessages("messages." + lang))
      }.toMap
        .+("default" -> loadMessages("messages"))
        .+("default.play" -> loadMessages("messages.default"))
    }
  }
  
  lazy val langs: Langs = new DefaultLangs(configuration)

}