apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/spi/oidc/ExcludeClientCredentialsClientRegistrationRepository.java/ExcludeClientCredentialsClientRegistrationRepository/findByRegistrationId
class ExcludeClientCredentialsClientRegistrationRepository:  @Override
  public ClientRegistration findByRegistrationId(String registrationId) {
    ClientRegistration clientRegistration = this.delegate.findByRegistrationId(registrationId);
    if (clientRegistration == null) {
      return null;
    }
    if (AuthorizationGrantType.CLIENT_CREDENTIALS
        .equals(clientRegistration.getAuthorizationGrantType())) {
      return null;
    }
    return clientRegistration;
  }