Checking in on main + 3.0.x docs and docker

Andrea and I worked a bit on the build server, and GitHub workflows, with the following success:

Docs

Documentation version selector is working, and docs are published for:

With both latest and stable available I tried to make each landing guide landing page consistently report {{version}} and {{release}} numbers.

The documentation workflow now validates for broken links.

aside: I have a suggestion on how the version selector should look here if anyone cares to comment.

Build

Andrea got geoserver-main-nightly working again, and I did some troubleshooting on the downstream docker-release job. The result is you can now work with:

docker pull docker.osgeo.org/geoserver:3.1.x
docker run -it -p 8080:8080 docker.osgeo.org/geoserver:3.1.x