Add "Unshare case" feature

Is your feature request related to a problem? Please describe. When drafting query cases, I can start sharing them with a team, but later change my mind. Currently Quepid only allows one-way sharing, but no unsharing functionality is available.

Describe the solution you'd like Flip "Share case" to "Unsare case" if it is shared.

Describe alternatives you've considered First cloning, then deleting the shared case could be one workaround.