Scenario for a single space restore from backup

## Is your feature request related to a problem? Please describe.

In the lifetime of an ownCloud instance, it can happen that users delete data which should not be deleted. Even despite the "two
-step" process through the trashbin, it has happened and will happen again. In these cases, a sysadmin team is often ask to restore only a part of the storage snapshot without a full "overwrite from backup"

## Describe the solution you'd like

1) Inside the product, which means a new backend feature
2) Additional tooling to work with the storage

## Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

## Additional context
Add any other context or screenshots about the feature request here.