optional opt-in for an automatic detach of timeshift to the storage repository

[nbehrnd]

Is your feature request related to a problem? Please describe.
An external hard drive is used to store the backups of timeshift. Contrasting to other backups for user data (e.g., vorta), once timeshift completed to create a snapshot, it does not detach from the external hard disk. Instead, I have to stop timeshift manually, and umount the drive with elevated user privileges of the super user.

Describe the solution you'd like
I would welcome there were either

• an option to unmount the external hard disk with user permissions of a normal (non-sudo) privileges, .or.
• an option to instruct timeshift in lines of of a rule like «if the next scheduled e.g., daily snapshot is 23+ hours away, the external storage repository is unmounted automatically once the current snapshot in progress is recorded completely».

Additional context
The observations refer to timeshift 21.09.1 as provided by the repositories of Linux Debian 12/bookworm (branch testing).