* Tweak - Ensure calling `Event_Tracking::custom_event()` records the event in GA4 in addition to UA
* Fix - Prevent a circular reference loop to cause out of memory errors in the integrations page if an auth token cannot be refreshed
* Fix - Correctly handle tracking of added shipping info events for orders without a shipping method set
* FIx - Restore and deprecate `Integration::custom_event()` in favor of `Event_Tracking::custom_event()`
