Checkout Additional fields not validated if required in Store API

[senadir]

When you have a required custom field in contact or additional, it doesn't get validated when you place a Store API order and it seems to be ignored.

Steps to reproduce:

• Add the following field via code:

add_action(
	'woocommerce_loaded',
	function() {
		__experimental_woocommerce_blocks_register_checkout_field(
			array(
				'id'       => 'plugin-namespace/job-function',
				'label'    => 'What is your main role at your company?',
				'location' => 'contact',
				'required' => true,
				'type'     => 'text'
			)
		);
	}
);

• In a REST client, add an item to cart, then head to Checkout and place the following the order:

{
	"billing_address": {
		"first_name": "test",
		"last_name": "test",
		"company": "",
		"address_1": "test",
		"address_2": "",
		"city": "test",
		"state": "",
		"postcode": "cb241ab",
		"country": "GB",
		"phone": "",
		"email": "testaccount@test.com"
	},
	"shipping_address": {
		"first_name": "test",
		"last_name": "test",
		"company": "",
		"address_1": "test",
		"address_2": "",
		"city": "test",
		"state": "",
		"postcode": "cb241ab",
		"country": "GB",
		"phone": ""
	},
	"payment_method": "bacs",
	"additional_fields": []
}

• Notice that you can place an order just fine, regardless if plugin-namespace/job-function is required or not.

Expected behavior

The order placing should reject.

[senadir]

Once this is fixed this test should be unskipped test_place_order_required_contact_field