withFieldGroup is a very powerful API! It'd be nice to modify entire group of fields at once - either
replace all of them with another value or reset all fields at once.

Perhaps we can edit new methods on group property obtained in the render property of withFieldGroup:

• group.resetAllFields which will reset all fields to their default values. Alternatively, if no argument is passed to group.resetField it'd reset all fields.
• group.replaceAllFields which will accept a single argument to replace all available fields at one go!

It'd be super helpful in case the groups are fuill.

In my specific use case, my team uses discriminated unions and it's a bit of an hassle to manually delete and add fields on each discriminator key change.

Another suggestion:

• group.deleteAllFields could also be an API or if no argument is passed to group.deleteField it'd delete all fields