Adding External Storage (SMB/CIFS) by using UNC path from LDAP attribute

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Is your feature request related to a problem? Please describe.
I have multible users which have their home directories located on different SMB/CIFS servers. The location of their home directories is stored as UNC path in a LDAP attribute. Right now the External Storage GUI has three separate text fields for 'server', 'share' and 'folder path', while the LDAP attribute has it 'all in one' like "\\server\share\path\to\folder". I know that I can use $user and $home variables but I can't use them with a full UNC path.

Describe the solution you'd like

1. Ability to add external storage (SMB/CIFS) using a UNC path
2. Ability to map the LDAP attribute containing the UNC path to a variable like "$path" or "$unc"

Describe alternatives you've considered
Ability to split UNC path into 'server', 'share' and 'folder path' parts and store them in new, separate variables.

Additional context
Already consulted Google and searched in the issues of this repository, but I didn't find anything like this.

The issue names Nextcloud's External Storage SMB/CIFS configuration and LDAP attribute mapping, but no files or tests. Start by locating the code for SMB/CIFS storage fields and LDAP-derived variables; done means accepting a complete UNC path and making the mapped LDAP value usable in that configuration.