docs: @Scheduled(fixedRate = 60000) // run every minute
  	public void invalidateOldTokens() {
  		List<String> invalidTokens = new ArrayList<String>(); // tokens to invalidate
  		for (Map.Entry<String, TokenContainer> entry : tokens.entrySet()) {
  			if (!entry.getValue().isValid()) {
  				invalidTokens.add(entry.getKey());
  			}
  		}
  		for (String token : invalidTokens) {
  			logout(token);
  		}
  	}