feat(devmanual): clean up the new release notes

[ChristophWurst]

☑️ Resolves

Follow-up to #14183 and #14565

This brings the Release notes into the final structure I had in mind with #14180

• There is one very prominent entrypoint for changes in this release
• There is one dedicated page for critical changes.
  • These have to be addressed. It's cleared after branch-off because afterwards it is no longer relevant.
• There is one dedicated page for new APIS.
  • These are nice-to-have for devs, nothing terrible happens if that page is not read.
  • The APIs will have their main documentation on a persistent page. This is just an overview here.
  • It's cleared after branch-off because afterwards it is no longer relevant.
• There is one collecting page for deprecations.
  • These are nice-to-have for devs, nothing terrible happens if that page is not read.
  • They stay there as long as they are relevant, so until they are removed.

The old upgrade guides stay for now and will phase out. Maybe we hand-pick the deprecations and move them to the new file. I'm too lazy for that right now.
There is a redirect rule to send anyone from the 34 page to the new pages.

🖼️ Screenshots

Entry point	Critical	New	Deprecated	Legacy

[nickvergessen]

should not forget to remove this after branch off? :P

[ChristophWurst]

It wouldn't do any harm, right? But yes can be removed at some point

[ChristophWurst]

The single purpose of this redirect is for someone who has already visited https://docs.nextcloud.com/server/latest/developer_manual/app_publishing_maintenance/app_upgrade_guide/upgrade_to_34.html to get sent to the new pages instead of a 404.

[skjnldsv]

Sure! 👍

[susnux]

Nice but I think this is a bit confusing to have another section split across the documentation.
Why not move all old notes to this new section as well like:

• Release notes
  • Critical changes
  • New in this version
  • Deprecations
  • Previous notes

We can still make the old links work with the redirects we already have in place for SEO.

[ChristophWurst]

Sounds good to move them to this place and add redirects 👍