Observe mounted, unlocked vaults and react to external unmounts

[infeo]

Summary

If a vault is mounted in the filesystem anymore (due to external events), it should be locked. The gui should react to such events, such that users are not mislead by showing the vault still as unlocked.

Motivation

Unlocking a vault in Cryptomator consists of two steps: Actually unlocking the cryptofilesystem and mounting the filesystem in the OS. While the first step is an internal procedure of the application, the second step interacts with the OS and third parties. As a consequence so created mounts can also be unmounted by external (aka non-Cryptomator) commands/events.

An example is MacOS: A vault mounted via Fuse shows in the volume section of the Finder (default system file manager). Finder allows to eject such volumes, which unmounts them and the content is no longer accessible. In Cryptomator, an ejected vault is still shown as unlocked.

Dokany- and Fuse-based Vaults can be easily monitored, because the main method to mount the vault is blocking, and hence it should be no problem implementing the feature. For WebDAV a research needs to be done, if and how this observe mechanism can be implemented.

Considered Alternatives

Remount the vault - A very bad idea, it could lead to a constant mount and unmount loop. Additionally, maybe the user inititated the unmount.

[infeo]

Depends on cryptomator/dokany-nio-adapter#49 and cryptomator/fuse-nio-adapter#46