code: public String processProjectId(String projectId) {
      if (projectId == null || projectId.trim().isEmpty() || projectId.equals(APPENGINE_CONFIG)) {
        throw new IllegalArgumentException(PROJECT_ERROR);
      } else if (projectId.equals(GCLOUD_CONFIG)) {
        return configReader.getProjectId();
      }
      return projectId;
    }
docs: Process user configuration of "projectId". If set to GCLOUD_CONFIG then read from gcloud's
  global state. If set but not a keyword then just return the set value.