code: @Override
  	public IdentifyingToken validate(IdentifyingToken token, @Nullable ChargingStationId chargingStationId) {
  		if (chargingStationId == null) {
              LOG.warn("No charging station id passed to validation request for token {}", token.getToken());
  			return token;
  		}
  
          ChargingStation chargingStation = repository.findOne(chargingStationId.getId());
  
  		if (chargingStation == null) {
  		    LOG.warn("Charging station not found in repository: {}", chargingStationId);
  			return token;
  		}
  
  		List<String> chargingStationAuthorizationProviders = chargingStation.getAuthorizationProvidersAsList();
  
  		if (chargingStationAuthorizationProviders.isEmpty()) {
  		    LOG.warn("No authorization providers configured for charging station: {}", chargingStationId);
  		    return token;
          }
  
          for (String authorizationProvider:chargingStationAuthorizationProviders) {
              AuthorizationProvider provider = providers.get(authorizationProvider);
  
              if (provider != null) {
                  IdentifyingToken validatedToken = provider.validate(token, chargingStationId);
                  if (validatedToken.isValid()) {
                      return validatedToken;
                  }
              }
          }
  
  		return token;
  	}
docs: Validates the token with the configured authentication providers for the charging station, as soon
  as one provider provides valid authorization this will be the result.
  
  @param token identifying token for which authorization is required
  @return validated IdentifyingToken