code: private static String createStorageKey(String userName, String remoteAddress) {
  
          StringBuffer result = new StringBuffer();
          result.append(userName);
          result.append(KEY_SEPARATOR);
          result.append(remoteAddress);
          return result.toString();
      }
docs: Returns the key to use for looking up the user in the invalid login storage.<p>
  
  @param userName the name of the user
  @param remoteAddress the remore address (IP) from which the login attempt was made
  
  @return the key to use for looking up the user in the invalid login storage