[Feature]: Indeterminate checkbox value with AutoForm

[modbender]

Describe the feature

I want to use indeterminate checkbox value with AutoForm, but I don't see any native way to do this yet. Requires modifying component.

I'm imagining something like setting props checkedValue and uncheckedValue, by default it will be boolean but it can be made to use string or other type of values. Setting indeterminateValue switches on indeterminate on checkbox.

Use case: supposedly in an advanced search of books, I want to filter genre of the books. I want to include some genres, I don't care about some genres and I want to exclude some genres from results.

include -> checked
don't care -> unchecked
exclude -> indeterminate

Additional information

• I intend to submit a PR for this feature.
• I have already implemented and/or tested this feature.