Return a string that represents the overall refund policy for all the items
in the shopping cart. See the support documentation for more details on
these policies:

https://en.support.wordpress.com/refunds/

@param {Object} cart - cart as `CartValue` object
@returns {string} the refund policy type
function getRefundPolicy( cart ) {
	if ( cartItems.hasDomainRegistration( cart ) && cartItems.hasPlan( cart ) ) {
		return 'planWithDomainRefund';
	}

	if ( cartItems.hasDomainRegistration( cart ) ) {
		return 'domainRefund';
	}

	return 'genericRefund';
}