Samba as a storage backend

## Is your feature request related to a problem? Please describe.
I would like to replace the nextcloud of a local non-profit with ocis. The nextcloud is used for mostly one thing: Accessing files stored in a samba share which belongs to a ldap user.

## Describe the solution you'd like
I'd like to have an option to use samba as a storage backend where not only the home of the user is a samba share but also more directories can be mounted to specific paths.
For example:
- The user home is: `\\server\user-homes\$USERNAME` -> mounted to `/`
- Some shared folders are at: `\\server\shares` -> mounted to `/shares`