docs: private void addContender(EmbeddedLeaderElectionService service, LeaderContender contender) {
  		synchronized (lock) {
  			checkState(!shutdown, "leader election service is shut down");
  			checkState(!service.running, "leader election service is already started");
  
  			try {
  				if (!allLeaderContenders.add(service)) {
  					throw new IllegalStateException("leader election service was added to this service multiple times");
  				}
  
  				service.contender = contender;
  				service.running = true;
  
  				updateLeader().whenComplete((aVoid, throwable) -> {
  					if (throwable != null) {
  						fatalError(throwable);
  					}
  				});
  			}
  			catch (Throwable t) {
  				fatalError(t);
  			}
  		}
  	}