code: public Connector createConnector(Long chargingStationTypeId, Long evseId, Connector connector) {
          ChargingStationType chargingStationType = chargingStationTypeRepository.findOne(chargingStationTypeId);
          Evse evse = getEvseById(chargingStationType, evseId);
          Set<Connector> originalConnectors = ImmutableSet.copyOf(evse.getConnectors());
  
          evse.getConnectors().add(connector);
  
          chargingStationType = chargingStationTypeRepository.createOrUpdate(chargingStationType);
  
          Set<Connector> newConnectors = getEvseById(chargingStationType, evseId).getConnectors();
          Set<Connector> diffConnectors = Sets.difference(newConnectors, originalConnectors);
  
          if (diffConnectors.size() == 1) {
              return Iterables.get(diffConnectors, 0);
          } else {
              return null;
          }
      }
docs: Creates a connector in a charging station type evse.
  
  @param chargingStationTypeId    charging station identifier.
  @param evseId                   evse id.
  @param connector                connector to be created.
  @return created connector.