Memorized cell location database (from location menu) is not correctly backed up/restored by seedvault

[symphorien]

Describe the bug
When restoring a seedvault backup of microg companion, the database of memorized cell tower/wifi access point locations is incorrectly empty.

To Reproduce
Steps to reproduce the behavior:

1. On phone 1, populate the wifi/cell tower database
2. back it up with seedvault
3. import the backup on phone 2
4. micro g companion > location > three dot menu > export database > the database is empty

Expected behavior
The database of the previous phone should be restored

System
Android Version: phone1: 15, phone2: 16
Custom ROM: phone 1: Calyxos 6.7 phone2: Calyxos 7.2

Additional context

Seedvault reports backup of microg companion with a green tick. This suggests that the data voluntarily reported by microg companion as backup does not include all the data worth a backup. https://github.com/seedvault-app/seedvault/wiki/Known-Issues#many-apps-dont-test-or-even-disable-backups