Stops working with number of variations over 30

[yakovsh]

Original issue here:
https://wordpress.org/support/topic/wc-external-variations-an-error-has-occured-see-console/

Root cause is the fact that WooCommerce doesn't export variation data over 30 and uses AJAX instead to load it from the server:
https://github.com/woocommerce/woocommerce/blob/trunk/includes/wc-template-functions.php#L1668
https://wordpress.org/support/topic/woocommerce-data-product_variationsfalse-doesnt-show-autmatically/

$get_variations = count( $product->get_children() ) <= apply_filters( 'woocommerce_ajax_variation_threshold', 30, $product );

[yakovsh]

For now, will document this and point users to a workaround using the "woocommerce_ajax_variation_threshold" filter:
https://docs.woocommerce.com/document/change-limit-on-number-of-variations-for-dynamic-variable-product-dropdowns/