When use Clientside Validation, required field is not validated before submit

Problem/Motivation

When I have Clientside Validation (clientside_validation) module enabled and have a required attribute on the phone field, clientside validation is not triggered.

Steps to reproduce

1. Install clientside_validation
2. Create a custom form with a phone field and some other required fields
#type => phone_international,
#required => true,
3. Try to submit the form without filling any fields

Expected result
All fields are highlighed

Actual result:
Phone field is not highlighed until real submission.

Proposed resolution

We need to proxy required attribute to subfields in order to be picked up by clientside_validation

Remaining tasks