Previous button triggers validation (when not using jQuery)

[skttl]

In a multipage setup, using aspnet-validation.js instead of jquery validation, the Previous button triggers validation, thus preventing the user in navigating to the previous page without meeting the validation criteria.

I would expect it to not try to validate, and simply go to the previous page. That is what it does, when using jquery-validate.

This has been seen in Forms 9.3.0 and 8.9.1.

To reproduce:
Create a form with multiple pages, make sure there are mandatory fields on all pages.
Render the form with aspnet-validation.js (not sure if @Html.RenderUmbracoFormDependencies() does that by default)
Fill in the fields to go to page 2.
Don't fill in fields on page 2 and try to click Previous.
The form will try to validate itself, and prevent going to previous page if validation fails.

[AndyButland]

I've created a PR to add support for this in the aspnet-validation.js library. If accepted, we can update forms to reference this version and add support for this via adding formnovalidate attribute to the previous page submit button.

[AndyButland]

The PR was accepted and so we've taken a dependency on this updated version of the library, which allows us to then include formnovalidate on the previous submit button in the default theme (or for anyone to add it to their custom themes).