code: private SnsMessage.Builder<? extends SnsMessage.Builder> unmarshallSubscriptionConfirmation(SnsJsonNode message) {
          return SnsSubscriptionConfirmation.builder(client)
                                            .withSubscribeUrl(message.getString(SUBSCRIBE_URL))
                                            .withToken(message.getString(TOKEN))
                                            .withMessage(message.getString(MESSAGE));
      }
docs: Unmarshall into a {@link SnsSubscriptionConfirmation} object.
  
  @param message JSON message.
  @return Builder with sub properties filled in. Base properties are added by
  {@link #unmarshallBase(SnsMessage.Builder, SnsJsonNode)}.