@Override
  public QuotaSource getQuotaSource() {
    return new DummyQuotaSource();
  }
Constructor for {@link DummyQuotaSourceFactory}.
@param quotaConfig {@link QuotaConfig} object.
@param accountService {@link AccountService} object.
@param quotaMetrics {@link QuotaMetrics} object.
@param routerConfig {@link RouterConfig} object.
ambry-test-utils/src/main/java/com/github/ambry/quota/DummyQuotaSourceFactory.java