external storage: photo-scan bug

Describe the bug
when using external storage: you have to run the initial maps:scan-photos for every user

To Reproduce
Steps to reproduce the behavior:

1. create an external storage folder with photos with gps-tag in it for more than one user
2. scan the photos for one specific user with occ maps:scan-photos userid
3. the photos appear only for that specific user in the maps app

Expected behavior
the scanned photos should appear for all users with access to the external storage folder

Desktop (please complete the following information):
Nextcloud 17.0.2
maps app 0.1.4

Additional context
The problem with that is, if you have a large external storage folder, with many photos, you had to scan this folder for every user again, which is not that efficient.
So a better way would be connecting the information to the external storage id -> so if you have access to that external storage folder, you will automatically see the photos on the map, if they were scanned before - no matter with which userid you have scanned that folder.

BTW: I guess the same problem would appear while using the groupfolders-app

Start by tracing the occ maps:scan-photos userid entry point and how scanned photos are associated with external storage access. Reproduce with one external folder shared by multiple users, then verify that a single scan makes the photos visible to every user with access, including a group folder if supported.