code: @Override
      public String getUserRegistryType() {
          synchronized (userRegistrySync) {
              if (isFederationActive && userRegistry != null) {
                  return FEDERATION_REGISTRY_TYPE;
              }
          }
          if (registryTypes.isEmpty() || registryTypes.size() > 1) {
              return UNKNOWN_TYPE;
          } else {
              return registryTypes.get(0);
          }
      }
docs: {@inheritDoc}