Default ProxyServlet cannot proxy to https urls

[joakime]

Jetty version
9.4.x

Description
If you have a default proxy setup like this ...

WEB-INF/web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" 
metadata-complete="false" 
version="3.0">

  <display-name>Transparent Proxy WebApp</display-name>

  <servlet>
    <servlet-name>JavadocTransparentProxy</servlet-name>
    <servlet-class>org.eclipse.jetty.proxy.ProxyServlet$Transparent</servlet-class>
    <init-param>
      <param-name>proxyTo</param-name>
      <param-value>https://www.eclipse.org/jetty/javadoc/</param-value>
    </init-param>
    <init-param>
      <param-name>hostHeader</param-name>
      <param-value>www.eclipse.org</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
    <async-supported>true</async-supported>
  </servlet>

  <servlet-mapping>
    <servlet-name>JavadocTransparentProxy</servlet-name>
    <url-pattern>/current/*</url-pattern>
  </servlet-mapping>

</web-app>

Then the ProxyServlet will fail as the internal HttpClient has no support for SSL/TLS enabled.

[joakime]

Talked with @sbordet and we'll just enable a default SslContextFactory.Client within AbstractProxyServlet.newHttpClient()

But do we want to introduce a newSslContextClient() method?

[joakime]

PR #5363 merged.