feat: Add Canonical Link Relation to stable branch to all manuals

[joshtrichards]

☑️ Resolves

• Fix Add canonical tags in pages linking to 'stable'; and add a warning for users. #9634 item one (item two will be in the next PR and is independent)

Should be backported as far back as possible so that all published (ancient) documentation versions pick this up (may also need to trigger new deploys for those; not sure if they still get picked up automatically).

Will probably require at least one manual backport PR when going beyond <stable32 due to conf.py formatting changes.

Refs:

• https://www.sphinx-doc.org/en/master/usage/configuration.html#confval-html_baseurl

🖼️ Screenshots

[joshtrichards]

Build issue is unrelated: nextcloud/server#54822 (comment)

[jospoortvliet]

Looks good to me! Stable is indeed a decent choice. Latest could be confusing with new features being there.

[joshtrichards]

/backport to stable32

[joshtrichards]

/backport to stable31

[joshtrichards]

Will see how the stable31 backport goes before triggering others. Will manually do that if it is necessary than backport to <v31 from that manually backported PR.

[backportbot]

The backport to stable31 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable31
git pull origin stable31

# Create the new backport branch
git checkout -b backport/13646/stable31

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick 4def5a71 610f02ff 753fbb66

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/13646/stable31

Error: Failed to check for changes with origin/stable31: No changes found in backport branch

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Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.