perf(2meet-data-optimizer-hivepress-addon): expire object-cache transients

- with an external object cache, a HivePress timeout entry expires when it
  records; the value (written before its timeout) after at most a week — a
  miss only makes HivePress rebuild it. Entries of deleted posts no longer
  accumulate without end
- Verify: HivepressTransientFilterTest TTL test, integration 53, unit 145;
  dev36 Redis TTL on tmdo_hp_transient keys
- PR: PR-099

includes/class-tmdo-hivepress-transient-filter.php

@@ -80,6 +80,9 @@ final class TMDO_Hivepress_Transient_Filter {
 	/** Object cache group used instead of wp_options when a persistent cache is present. */
 	public const CACHE_GROUP = 'tmdo_hp_transient';
 
+	/** Longest an object-cache entry lives: a week (HivePress's default is a day). */
+	public const MAX_CACHE_TTL = 604800;
+
 	/**
 	 * Register the four metadata filters on `init`. Idempotent — safe to call
 	 * multiple times.
@@ -267,8 +270,10 @@ final class TMDO_Hivepress_Transient_Filter {
 	 * In wp_options both halves of the transient pair are written with
 	 * `autoload=no` (they are read on-demand only — never via
 	 * wp_load_alloptions() — so eagerly loading them on every page would defeat
-	 * the point of the move). HivePress checks the timeout itself, so the
-	 * cache entries get no TTL of their own.
+	 * the point of the move). In the object cache a timeout entry expires when
+	 * it says; the value, written before its timeout, after MAX_CACHE_TTL — a
+	 * miss only makes HivePress rebuild it — so entries of deleted posts do
+	 * not pile up (2.3 PR-099).
 	 *
 	 * @param int    $post_id    Post ID.
 	 * @param string $meta_key   Original `_transient_*` meta_key.
@@ -281,7 +286,8 @@ final class TMDO_Hivepress_Transient_Filter {
 		$option_name = ( $is_timeout ? '_transient_timeout_' : '_transient_' ) . $translated;
 
 		if ( wp_using_ext_object_cache() ) {
-			wp_cache_set( $option_name, $meta_value, self::CACHE_GROUP );
+			$ttl = $is_timeout ? min( self::MAX_CACHE_TTL, max( 1, (int) $meta_value - time() ) ) : self::MAX_CACHE_TTL;
+			wp_cache_set( $option_name, $meta_value, self::CACHE_GROUP, $ttl );
 			return;
 		}
 		update_option( $option_name, $meta_value, false );