Store event date and time in event meta data

[brendt]

To find out when an event was originally dispatched, you need to run the following code:

        $checkedOutAt = Carbon::make(
            EloquentStoredEvent::find($event->storedEventId())->created_at
        );

It's easier to store the created_at timestamp in the event's meta data as well, so that we can do this:

$event->createdAt()