Use page_published signal for cache invalidation instead of post_save

wagtail/contrib/wagtailfrontendcache/signal_handlers.py

@@ -1,12 +1,13 @@
 from django.db import models
-from django.db.models.signals import post_save, post_delete
+from django.db.models.signals import post_delete
 
 from wagtail.wagtailcore.models import Page
+from wagtail.wagtailcore.signals import page_published
 
 from wagtail.contrib.wagtailfrontendcache.utils import purge_page_from_cache
 
 
-def post_save_signal_handler(instance, **kwargs):
+def page_published_signal_handler(instance, **kwargs):
     purge_page_from_cache(instance)
 
 
@@ -20,5 +21,5 @@ def register_signal_handlers():
 
     # Loop through list and register signal handlers for each one
     for model in indexed_models:
-        post_save.connect(post_save_signal_handler, sender=model)
+        page_published.connect(page_published_signal_handler, sender=model)
         post_delete.connect(post_delete_signal_handler, sender=model)