Provide an unsetCurrentContext method ?

Relates to #61

Provide a way to programmatically delete the `ims.config.current` config without having to use `aio-lib-config`.
This can be used to reset the context back to the default CLI context in a desktop environment

We should also expose this in the auth plugin

Start by locating how `ims.config.current` is set and cleared, then inspect the auth plugin integration mentioned in the issue. Done means exposing a programmatic unset method that restores the default CLI context and making it available through the auth plugin.

Written by the indexing model from the issue text.