[QA](7.4.z) UNDERTOW-2116 - java.lang.AssertionError: Content-Encoding header should be defined

<subsystem xmlns="urn:jboss:domain:undertow:12.0" default-server="default-server" default-virtual-host="default-host" default-servlet-container="default" default-security-domain="other" statistics-enabled="${wildfly.undertow.statistics-enabled:${wildfly.statistics-enabled:false}}">
            <buffer-cache name="default"/>
            <server name="default-server">
                <http-listener name="default" socket-binding="http" redirect-socket="https" enable-http2="true"/>
                <https-listener name="https" socket-binding="https" security-realm="ApplicationRealm" enable-http2="true"/>
                <host name="default-host" alias="localhost">
                    <location name="/" handler="welcome-content"/>
                    <access-log/>
                    <filter-ref name="gzip-filter"/>
                    <http-invoker security-realm="ApplicationRealm"/>
                </host>
            </server>
            <servlet-container name="default">
                <jsp-config/>
                <websockets/>
            </servlet-container>
            <handlers>
                <file name="welcome-content" path="${jboss.home.dir}/welcome-content"/>
            </handlers>
            <filters>
                <gzip name="gzip-filter"/>
            </filters>
        </subsystem>

 @Test
    public void gzipDefaultAsOnDemandBehaviourTest(@ArquillianResource URL url) throws  {
        String targetUrl = url.toExternalForm() + "index.html";

        HttpHead standardRequest = new HttpHead(targetUrl);

        HttpHead gzipExplicitRequest = new HttpHead(targetUrl);
        gzipExplicitRequest.addHeader(Headers.ACCEPT_ENCODING_STRING, "gzip");

        HttpHead gzipDeflateExplicitRequest = new HttpHead(targetUrl);
        gzipDeflateExplicitRequest.addHeader(Headers.ACCEPT_ENCODING_STRING, "gzip");
        gzipDeflateExplicitRequest.addHeader(Headers.ACCEPT_ENCODING_STRING, "deflate");

String compressionType="gzip";

       try (CloseableHttpClient httpClient = HttpClientBuilder.create().disableContentCompression().build()) {
            CloseableHttpResponse response = httpClient.execute(gzipDeflateExplicitRequest);
            Assert.assertEquals(HttpURLConnection.HTTP_OK, response.getStatusLine().getStatusCode());
            Header contentEncodingHeader = response.getFirstHeader(Headers.CONTENT_ENCODING_STRING);
   
            Assert.assertNotNull("Content-Encoding header should be defined", contentEncodingHeader);
           Assert.assertEquals("Content-Encoding header should be defined with value '" + compressionType.toLowerCase() + "'",
                    compressionType.toLowerCase(), contentEncodingHeader.getValue().toLowerCase());
        }
    }