Javadoc generation

[Konrad Windszus]

I am currently looking for a documentation how the javadoc for a Sling release 
is generated. The documentation at 
https://sling.apache.org/documentation.html#the-javadoc seems to be outdated. I 
want to make sure that for Sling9 we include some more packages here: 
https://issues.apache.org/jira/browse/SLING-6766.
Thanks for any pointers.
Konrad