Improve redirect detection for javadocs

[kwin]

New feature, improvement proposal

Currently the given externalJavadocBaseUrl is being used first to construct a target url (e.g. to element-list) and then it is requested. This fails when there is no deep redirect support. For example the Oracle URL https://docs.oracle.com/javase/11/docs/api/ redirects to https://docs.oracle.com/en/java/javase/11/docs/api/index.html but https://docs.oracle.com/javase/11/docs/api/element-list is also redirected to https://docs.oracle.com/en/java/javase/11/docs/api/index.html instead of https://docs.oracle.com/en/java/javase/11/docs/api/element-list.

In order to support redirects which always redirect to the index page, the request url should be constructed after the redirect target has been been resolved.

This requires some change in

maven-plugin-tools/maven-plugin-tools-api/src/main/java/org/apache/maven/tools/plugin/javadoc/JavadocSite.java

Line 539 in 4ee91b1

if (pos >= 0 && isNotEmpty(redirects)) {

.