Partially automate 100% deploy percentage detection

[joshtrichards]

With the new json based config builder introduced for Server's updater_server in nextcloud-releases/updater_server#1053 we are closer to being able to more easily detect upstream deploy % changes for the latest major.

We should look at implementing a workflow that detects when the deploy percentage is changed from <100% to trigger bumping our stable and production tags that then, to start, creates either an associated PR for review (with the version change) or, at a minimum, a tracking issue.

P.S. A simpler but similar workflow could be used for automatically detecting maintenance releases (without regard to deploy %).

Related: #2265

[khassad]

Sounds great !
From my understanding, the current process is manual, we rely on someone, J0WI this time, to make a manual PR and the code owners to validate it.

From this point the release process and push to Docker Hub is automated ?

[tianon]

In case you're considering automating PRs to DOI, https://github.com/docker-library/faq#can-i-use-a-bot-to-make-my-image-update-prs might be relevant.