: stream_info_(server_context.timeSource(), nullptr,

                   StreamInfo::FilterState::LifeSpan::FilterChain) {

  ASSERT_IS_MAIN_OR_TEST_THREAD();

  Server::GenericFactoryContextImpl generic_context{server_context,

                                                    server_context.messageValidationVisitor()};

  auto commands = Formatter::SubstitutionFormatStringUtils::parseFormatters(

      http_service.formatters(), generic_context);

  SET_AND_RETURN_IF_NOT_OK(commands.status(), creation_status);

  for (const auto& header_value_option : http_service.request_headers_to_add()) {

    const auto& header = header_value_option.header();

    if (!header.value().empty()) {

      auto formatter_or_error = Formatter::FormatterImpl::create(header.value(), false, *commands);

      SET_AND_RETURN_IF_NOT_OK(formatter_or_error.status(), creation_status);

      formatted_headers_.emplace_back(LowerCaseString(header.key()),

                                      std::move(formatter_or_error.value()));

    } else {

      static_headers_.emplace_back(LowerCaseString(header.key()), header.raw_value());

    }

  }

}

void HttpServiceHeadersApplicator::apply(RequestHeaderMap& headers) const {

  for (const auto& header_pair : static_headers_) {

    headers.setReference(header_pair.first, header_pair.second);

  }

  if (!formatted_headers_.empty()) {

    for (const auto& header_pair : formatted_headers_) {

      headers.setCopy(header_pair.first, header_pair.second->format({}, stream_info_));

    }

  }

}