requestHeaderBhv.insertOrUpdate(requestHeader, op -> {
            op.setRefreshPolicy(Constants.TRUE);
        });

    }

    /**
     * Deletes a request header configuration from the database.
     *
     * @param requestHeader the request header configuration to delete
     */
    public void delete(final RequestHeader requestHeader) {

        return asJson(new ApiResponse().status(Status.OK).result());
    }

    /**
     * Creates an EditBody from a RequestHeader entity.
     *
     * @param entity the request header entity to convert
     * @return the converted EditBody
     */
    protected EditBody createEditBody(final RequestHeader entity) {
        final EditBody body = new EditBody();
        copyBeanToBean(entity, body, copyOp -> {

        RequestHeaderService requestHeaderService = new RequestHeaderService() {
            @Override
            public List<RequestHeader> getRequestHeaderList(final String webConfigId) {
                return Collections.emptyList();
            }
        };
        ComponentUtil.register(requestHeaderService, RequestHeaderService.class.getCanonicalName());

        // request header
        final List<RequestHeader> requestHeaderList = requestHeaderService.getRequestHeaderList(getId());
        final List<org.codelibs.fess.crawler.client.http.RequestHeader> rhList = new ArrayList<>();
        for (final RequestHeader requestHeader : requestHeaderList) {
            rhList.add(requestHeader.getCrawlerRequestHeader());
        }

        // Request Header
        final RequestHeader[] requestHeaders = getInitParameter(REQUEST_HEADERS_PROPERTY, new RequestHeader[0], RequestHeader[].class);
        for (final RequestHeader requestHeader : requestHeaders) {
            if (requestHeader.isValid()) {
                requestHeaderList.add(new BasicHeader(requestHeader.getName(), requestHeader.getValue()));
            }
        }

        // Request Header
        final RequestHeader[] requestHeaders = getInitParameter(REQUEST_HEADERS_PROPERTY, new RequestHeader[0], RequestHeader[].class);
        for (final RequestHeader requestHeader : requestHeaders) {
            if (requestHeader.isValid()) {
                requestHeaderList.add(new BasicHeader(requestHeader.getName(), requestHeader.getValue()));
            }
        }

            count++;
            headerName = paramMap.get(CRAWLER_WEB_HEADER_PREFIX + count + ".name");
        }
        if (!rhList.isEmpty()) {
            factoryParamMap.put(HcHttpClient.REQUEST_HEADERS_PROPERTY,
                    rhList.toArray(new org.codelibs.fess.crawler.client.http.RequestHeader[rhList.size()]));
        }

- The `DeclarativeValidation` feature gate is enabled by default. When...