wp-proudcity#2829: gate GF Stripe rate-limiter disable on PC_DISABLE_GF_STRIPE_RATE_LIMIT env var

The filter is now applied only when the k8s pod is launched with
PC_DISABLE_GF_STRIPE_RATE_LIMIT=true. Default behaviour is the unmodified
GF Stripe rate limiter, so the workaround is opt-in per tenant via a
workload-YAML env var rather than platform-wide. Pairs with the launch
checklist note in pc-dev-issues/.github/ISSUE_TEMPLATE/launch.md and is
tracked for removal under pc-dev-issues#287.

Author: curtismchale

www/wp-content/mu-plugins/disable-gf-stripe-rate-limit.php

@@ -1,16 +1,24 @@
 <?php
 /**
  * Plugin Name: Disable GF Stripe IP Rate Limit
- * Description: Disables the Gravity Forms Stripe add-on per-IP rate limiter. Required while all
- *              customers share the same internal k8s IP from WordPress's perspective, which causes
- *              one customer's card errors to lock out every other customer for an hour.
- *              Remove once the k8s ingress forwards the real client IP to PHP.
+ * Description: Conditionally disables the Gravity Forms Stripe add-on per-IP rate
+ *              limiter when the k8s pod is launched with PC_DISABLE_GF_STRIPE_RATE_LIMIT=true.
+ *              Required while all customers share the same internal k8s IP from WordPress's
+ *              perspective (see pc-dev-issues#287), which causes one customer's card errors
+ *              to lock out every other customer for an hour. Set the env var per-tenant in
+ *              the deployment YAML so the override is opt-in and tracked, not platform-wide.
+ *              Once pc-dev-issues#287 lands, remove the env var from any pod that has it.
  * Author:      ProudCity
- * Version:     1.0.0
+ * Version:     1.1.0
  */
 
 if ( ! defined( 'ABSPATH' ) ) {
 	exit;
 }
 
-add_filter( 'gform_stripe_enable_rate_limits', '__return_false' );
+// getenv() is used (rather than $_ENV) so it works under PHP-FPM regardless of
+// variables_order. Compared strictly to the literal string "true" so an unset
+// or any other value leaves the rate limiter enabled.
+if ( getenv( 'PC_DISABLE_GF_STRIPE_RATE_LIMIT' ) === 'true' ) {
+	add_filter( 'gform_stripe_enable_rate_limits', '__return_false' );
+}