old_contents: from django.apps import AppConfig
  
  
  class WagtailMediaAppConfig(AppConfig):
      name = "wagtailmedia"
      label = "wagtailmedia"
      verbose_name = "Wagtail media"
  
      def ready(self):
          from wagtailmedia.signal_handlers import register_signal_handlers
  
          register_signal_handlers()
  
new_contents: from django.apps import AppConfig
  
  
  class WagtailMediaAppConfig(AppConfig):
      default_auto_field = 'django.db.models.AutoField'
      name = "wagtailmedia"
      label = "wagtailmedia"
      verbose_name = "Wagtail media"
  
      def ready(self):
          from wagtailmedia.signal_handlers import register_signal_handlers
  
          register_signal_handlers()
  
subject: Add default_auto_field