Have Client logout correctly

[aledomu]

Is your feature request related to a problem? Please describe. Currently if I logout the only thing I can do is drop Client, but that leaves any task running until it ends and it leaves the store in the disk.

Describe the solution you'd like Add a .logout() async method that handles this in the right way.

Describe alternatives you've considered Doing that as the user of this library, but then every client would have to implement this functionality again and makes its usage more difficult.

Additional context We need this in Fractal.