Prevent deleting all files

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Feature request

There will be a good option to prevent delete all files. I use this for backups also so if something is going worng and backup doesn't upload to nextcloud anymore than after x days all files will be deleted.
So an option to keep last X files instead of x days will be verry good.

Which Nextcloud Version are you currently using: (see administration page)
32
Is your feature request related to a problem? Please describe.
A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]
Yes this can delete all of my backup files.
Describe the solution you'd like
A clear and concise description of what you want to happen.
To have also option, keep last x files instead just days

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.
delete all opf my backup files
Additional context
Add any other context or screenshots about the feature request here.

Start by reading the feature request in issue #1002 and inspect the repository to find the existing retention-by-days entry point. Define and implement the option to keep the last X backup files, ensuring an interrupted upload cannot result in every backup being deleted; done means the retention behavior is covered by appropriate tests.