Support nextcloud-specific symbolic links

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

I have a nextcloud server with 2 accounts: account1 and account2.

account1 files structure:

/private
/private/photos
/common

account2 files structure:

/documents

I would like account1 to:

1. be able to create some kind of reference to the folder /private/photos inside /common:

/private
/private/photos
/common
/common/photos -> /private/photos

2. be able to share the folder /common, so that account2 sees the shared folder common inside which they can click on the folder reference photos and be redirected to the folder photos (with proper access control checks)

Describe alternatives you've considered
I didn't find any alternative

Additional context

To start with, maybe we could get rid of access control checks and simply consider that when a folder is shared, the folder references inside it inherit the access controls of the shared link

This has to be nextcloud-native because ideally the behavior is replicated in the app: when acocunt2 uploads a file to common/photos, it gets uploaded to account1//documents/private/photos

Maybe this référence could be directly translated to a symbolic link on the underlying filesystem, when compatible

The issue names no files, tests, or entry points. Start by mapping Nextcloud's existing sharing and filesystem-reference behavior, then define the access-control and upload semantics for references across shared folders. Done means a scoped implementation plan and tests covering navigation, permissions, and uploads.