Migrate the groovy extension for XWiki into a contrib extension in Java

Currently, we need specific code on XWiki to make it work with Cristal.

This code is written in groovy and is not distributed as a contrib extension, making it difficult to maintain and deploy.

A discussion was started to create a contrib extension for xwiki https://forum.xwiki.org/t/new-contrib-project-request-cristal-for-xwiki/13583

This work involves resuming the discussion to reach an agreement.