code: public static BoxDeveloperEditionAPIConnection getAppUserConnection(String userId, BoxConfig boxConfig) {
          return getAppUserConnection(userId, boxConfig.getClientId(), boxConfig.getClientSecret(),
                  boxConfig.getJWTEncryptionPreferences());
      }
docs: Creates a new Box Developer Edition connection with App User token levaraging BoxConfig.
  @param userId                the user ID to use for an App User.
  @param boxConfig             box configuration settings object
  @return a new instance of BoxAPIConnection.