Fix: FluentCart real-time orders ignore Selected Product filter

[AmitPaul-akp]

Summary

Real-time FluentCart orders trigger every enabled NotificationX sales campaign whose status matches the incoming order, regardless of the campaign's Show Purchase Of: Selected Product or Exclude Products settings. The product/category filter is only honored on the Regenerate path.

Reproduction

1. Create two FluentCart sales campaigns:
   • Campaign A -> Show Purchase Of: Selected Product -> Product A
   • Campaign B -> Show Purchase Of: Selected Product -> Product B
2. Click Regenerate on both - filter works correctly.
3. Place a live order for Product A via FluentCart.
4. Expected: only Campaign A fires.
   Actual: both Campaign A and Campaign B fire.

Root cause

FluentCart::nx_can_entry() - the only callback registered on nx_can_entry_fluentcart - checks order/payment/shipping/fulfillment status only. It does not apply _show_purchaseof() / _excludes_product().

Real-time orders flow through:

fluent_cart/order_paid_done -> save_new_records() -> parent::save() -> update_notification() -> apply_filters('nx_can_entry_fluentcart', ...)

...so live orders bypass the product filter entirely. The Regenerate path works because get_orders() calls _excludes_product() / _show_purchaseof() itself before constructing entries.

For comparison, the WooCommerce source registers two callbacks on the same filter - status check and the Conversions type's product filter - at WooCommerce.php:110-111. FluentCart only registered the status one.

Note: we can't just delegate to Conversions::nx_can_entry because that compares against post IDs, while FluentCart stores product list values as slugs (product_lists() keys by post_name). Reusing FluentCart's own _excludes_product() / _show_purchaseof() keeps slug semantics identical to Regenerate.

Fix

Extend FluentCart::nx_can_entry() to apply the same _excludes_product === _show_purchaseof condition that get_orders() already uses. Behavior is now consistent between Regenerate and real-time paths.

• Scope: 1 file, 1 method (nx_can_entry), +25 / -2.
• No new dependencies, no signature changes, no new files.
• Pro inline source (fluentcart_inline) inherits the fix via FluentCart::get_instance() reference - no Pro-side changes required.

Safety

• Status-only campaigns (no product_control, no product_exclude_by): _excludes_product returns false, _show_purchaseof returns true -> differ -> entry passes. No regression.
• Explicit 'none' / 'none' configs: returns true / false -> still differ -> entry passes. No regression.
• Pro inline entries without product_id: guarded with if ($product_id) -> falls through, original behavior preserved.
• get_the_terms() result guarded with is_wp_error() + !empty().
• php -l (PHP 8.2): clean.

Test plan

• Create two FluentCart sales campaigns with different Selected Product values
• Place a live order for the product selected in Campaign A -> only Campaign A fires
• Place a live order for the product selected in Campaign B -> only Campaign B fires
• Campaign with no product filter (status only) still fires for any matching order
• Campaign with Exclude Products set: excluded product does not trigger; non-excluded does
• Campaign with Product Category filter: orders for products in the selected category fire; others don't
• Regenerate continues to behave identically (no double-filtering regressions)
• FluentCart Pro inline source still renders correctly

Reported by client via Fluent Boards task #81314.