code: public void updateSubscribers(ChargingStation chargingStation, Date timestampStatusChange) {
          StatusChange change = new StatusChange(chargingStation.getId(), timestampStatusChange, chargingStation.getState(), chargingStation.getNumberOfFreeEvses());
  
          List<Subscription> subscriptions = subscriptionRepository.findAll();
          for (Subscription subscription : subscriptions) {
              executorService.execute(new SubscriptionUpdater(subscriberClient, subscription, change));
          }
      }
docs: Updates all known subscribers (from the repository) about the new state the charging station is in. Uses the executor
  service to execute updaters. Any exceptions thrown by an updater (e.g. client not reachable) will not influence
  other updaters.
  
  @param chargingStation charging station that had it's state changed.
  @param timestampStatusChange timestamp of the change