$validationGroups: there's not a way to group errors from nested forms.

[renatodeleao]

Describe the bug
If using nested forms, as described by documentation, the errors from nested forms are indeed caught by the parent component. But there no way (unless hand-rolled) to group those errors into $validationGroups. This is particularly important in stepped forms where errors are scoped (grouped) by step, and especially if those nested form are reusable component instances, that cannot be hardcoded into root form state.

Reproduction URL
https://codesandbox.io/s/multi-step-form-with-vuelidate-nested-forms-hrs266?file=/src/App.vue

To Reproduce
Steps to reproduce the behavior:

1. Go to 'step with nested form tab'
2. Type to validate on the "something" field, (see that $validationGroups catches the error and updates tab error count)
3. Type to validate on the nested form field
4. See error. Even if root form catches the error $validationGroups does not update to reflect nested errors.

Expected behavior
Expect that $validationGroups work with nested forms, either by passing the $registerAs path or the actual nested fields paths. But none of that works.