new interface to list snaps (snapd-observe)

[Gabriel Cocenza]

In the current project that I'm working, I need to list snaps that are installed in a machine. The task looks simple, but in order to use "snap list" it needs to be classic confinement. Another possibility is using the snapd-control interface, but using it just to list the available snaps is quite an overreach in terms of privileges.

During a store-request[0] it was said that it's possible to hack by accessing the content of /var/lib/snapd/state.json by using system-files, but there is no guarantee that developers will keep the structure of this file and it's a fragile way of getting this information in the long run.

I think it would be good having a new interface like snapd-observe where it's possible to get information, but it's not able to remove, install snaps and etc.

Thanks

[0] https://forum.snapcraft.io/t/manual-review-for-software-inventory-exporter-auto-connect-request-for-system-files-and-snapd-control/34363