Auto-backup folder selection with system dialog

[TheDoctorT]

Checklist

• I made sure that there are no existing issues - open or closed - to which I could contribute my information.
• I made sure that there are no existing discussions - open or closed - to which I could contribute my information.
• I have read the FAQs inside the app (Menu -> About -> FAQs) and my problem isn't listed.
• I have taken the time to fill in all the required details. I understand that the request will be dismissed otherwise.
• This issue contains only one feature request.
• I have read and understood the contribution guidelines.

Feature description

When selecting a path for the auto-backups some sort of app-internal file browser is used. Because of this, folders created by other apps cannot be seen. I suggest using the file browser of the system to select the location. This allows selecting any folder on the device. If the app doesn't have permission to open this location, the system file browser asks the user if the app should be given access to the location.

Why do you want this feature?

In my specific case I use Syncthing to backup my notes to a remote server. The folder used to belong to Notes. After a device reset Syncthing recreated the folder, which now can't be used for the backups by Notes anymore. But I believe the use cases for this feature are much broader than my personal experience.

Additional information

When exporting the notes the file browser used is already the system file browser, so I find the difference in handling curious. If you need an example of how this could work, Aegis Authenticator is the first FOSS app with a backup feature implemented the way I described.