Cache Invalidation (Global + Popular Cache Plugins)

Clears headers and triggers cache flush for popular WP caching plugins (W3TC, WP Fastest Cache, LiteSpeed Cache, Super Cache, etc.).

// "Soft" HTTP/cache layer cleaning:
CFGP_U::cache_flush();

// Force plugin transient clearing as well:
CFGP_U::cache_flush(true);

// Only plugin transients (REST cache etc.):
CFGP_U::flush_plugin_cache();