docs: public static boolean isValidFqcn(String str) {
      if (isNullOrEmpty(str)) {
        return false;
      }
      final String[] parts = str.split("\\.");
      if (parts.length < 2) {
        return false;
      }
      for (String part : parts) {
        if (!isValidJavaIdentifier(part)) {
          return false;
        }
      }
      return true;
    }