Add support for nullable Boolean parameters to enable a tri-state option

### Is your feature request related to a problem? Please describe.

I can't determine whether the parameter value is user-supplied or a default for Boolean type parameters, as they can only be `true` or `false`.

Hence, request to add support for nullable Boolean parameters to enable a tri-state option.

### Describe the solution you'd like.

Nullable Boolean parameters to enable a tri-state option.

The initial value of null, and it is assigned true or false based on user input. Remains as null if that parameter is not provided.

### Additional context

CLI boolean type parameters.