Nuxeo Release Promotion

With NXP-27996, we have a new Nuxeo build each time there is a merge/push on master.

When one of those builds is validated to be production-ready, we need to promote that build as a new release so that all artifacts can be available to be used on production:

• Docker images
• Maven artifacts
• Nuxeo packages

The nuxeo/nuxeo repository must be also updated:

• Create the maintenance branch for the first release.
• Update version on the maintenance or master branch.