code: public static OAuthRegisteredService getRegisteredOAuthServiceByClientId(final ServicesManager servicesManager, final String clientId) {
          return getRegisteredOAuthServiceByPredicate(servicesManager, s -> s.getClientId().equals(clientId));
      }
docs: Locate the requested instance of {@link OAuthRegisteredService} by the given clientId.
  
  @param servicesManager the service registry DAO instance.
  @param clientId        the client id by which the {@link OAuthRegisteredService} is to be located.
  @return null, or the located {@link OAuthRegisteredService} instance in the service registry.