Improve rendering of Order Attribution inputs (#44333)

- Expose public method to render OA input fields 
- Render OA inputs on `woocommerce_checkout_after_customer_details` 
   in case the checkout form does not contain `woocommerce_checkout_shipping`, `woocommerce_after_order_notes`.

Addresses part of #44159

Co-authored-by: Justin Palmer <228780+layoutd@users.noreply.github.com>
Co-authored-by: github-actions <github-actions@github.com>

plugins/woocommerce/changelog/44333-fix-44159-oa-missing-fields

@@ -0,0 +1,4 @@
+Significance: patch
+Type: update
+
+Move rendering of Order Attribution inputs to `woocommerce_checkout_after_customer_details`. Expose a method for custom theming.

plugins/woocommerce/src/Internal/Orders/OrderAttributionController.php

@@ -111,13 +111,8 @@ function() {
 			}
 		);
 
-		// Include our hidden `<input>` elements on order notes and registration form.
-		$source_form_elements = function() {
-			$this->source_form_elements();
-		};
-
-		add_action( 'woocommerce_after_order_notes', $source_form_elements );
-		add_action( 'woocommerce_register_form', $source_form_elements );
+		add_action( 'woocommerce_checkout_after_customer_details', array( $this, 'source_form_elements' ) );
+		add_action( 'woocommerce_register_form', array( $this, 'source_form_elements' ) );
 
 		// Update order based on submitted fields.
 		add_action(
@@ -347,10 +342,11 @@ private function output_origin_column( WC_Order $order ) {
 	}
 
 	/**
-	 * Add `<input type="hidden">` elements for source fields.
-	 * Used for checkout & customer register froms.
+	 * Print `<input type="hidden">` elements for source fields.
+	 * To be picked up and populated with data by the JS.
+	 * Used for checkout & customer register forms.
 	 */
-	private function source_form_elements() {
+	public function source_form_elements() {
 		foreach ( $this->field_names as $field_name ) {
 			printf( '<input type="hidden" name="%s" value="" />', esc_attr( $this->get_prefixed_field_name( $field_name ) ) );
 		}