docs: private RSAPublicKey getKeyForUser(String userName) throws KeyNotFoundException {
      RSAPublicKey key = null;
      for (final KeyProvider keyProvider : keyProviders) {
        try {
          key = keyProvider.getKey(userName);
          break;
        } catch (KeyNotFoundException e) {
          // that's fine, try the next provider
        }
      }
  
      if (key == null) {
        throw new KeyNotFoundException();
      }
  
      return key;
    }