Validate missing fields in Store API

[senadir]

Changes proposed in this Pull Request:

In additional fields, we would only validate passed fields, this means required missing fields would not get validated, this fixes it and enable the test for it.

Closes #45496

How to test the changes in this Pull Request:

Using the WooCommerce Testing Instructions Guide, include your detailed testing instructions:

1. Tests should pass.
2. Add the following snippet to your store

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' => 'additional',
				'required' => true,
				'type'     => 'text',
			)
		);
	}
);

3. Send this request to Store API after adding to cart:

{
	"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": {}
}

4. You should get an error saying the field is missing or not the correct type.

[github-actions]

Test Results Summary

Commit SHA: 1fd8e60

Test 🧪	Passed ✅	Failed 🚨	Broken 🚧	Skipped ⏭️	Unknown ❔	Total 📊	Duration ⏱️
API Tests	259	0	0	2	0	261	0m 38s
E2E Tests	344	0	0	37	0	381	9m 7s

---

To view the full API test report, click here.
To view the full E2E test report, click here.
To view all test reports, visit the WooCommerce Test Reports Dashboard.

[github-actions]

Hi @wavvves,

Apart from reviewing the code changes, please make sure to review the testing instructions as well.

You can follow this guide to find out what good testing instructions should look like:
https://github.com/woocommerce/woocommerce/wiki/Writing-high-quality-testing-instructions

[senadir]

This file has no changes.

[senadir]

Changes are starting from here.

[wavvves]

LGTM 👍🏼