@Override
  public QuotaSource getQuotaSource() {
    return source;
  }
Constructor to create a {@link JSONStringStorageQuotaSourceFactory}.
@param quotaConfig The {@link QuotaConfig} to use.
@param accountService The {@link AccountService} to use.
@param quotaMetrics The {@link QuotaMetrics} to use.
@param routerConfig The {@link RouterConfig} to use.
@throws IOException
ambry-quota/src/main/java/com/github/ambry/quota/storage/JSONStringStorageQuotaSourceFactory.java