Some fields do not require validation

Every time a FormZInput is defined we must add a validation error even if we never get to use it. Some fields do not require validation, but do require being inside the form to later verify if the field has changed its value.

Example:

// abstract class FormzInput<T, E>

enum StatusMemberInputError { none }

class StatusMemberInput extends FormzInput<bool, StatusMemberInputError> {
  const StatusMemberInput.pure({bool value = false}) : super.pure(value);

  const StatusMemberInput.dirty({bool value = false}) : super.dirty(value);

  @override
  StatusMemberInputError? validator(bool value) => null;
}

Start by locating the FormzInput definition and the code that requires a validation error for each input. Review the existing form and input tests, then make it possible for an input to participate in change tracking without requiring validation; done when the StatusMemberInput example is supported and the relevant tests pass.