docs: private void scanForUnknownDirectories() {
        File[] filesInRoot = rootDirectory.listFiles();
        if (filesInRoot != null) {
           for (File maybeDirectory : filesInRoot) {
              if (maybeDirectory.isDirectory()) {
                 String name = maybeDirectory.getName();
                 try {
                    getDirectory(name);
                 }
                 catch (PersistenceException e) {
                    log.couldNotWalkDirectory(name, e);
                 }
              }
           }
        }
     }