Send CRM contact ID to GA4 to enable user ID tracking

WP Fusion could easily grab the contact ID from logged in users and pass it to GA4: https://developers.google.com/analytics/devguides/collection/ga4/user-id?client_type=gtag

This would allow for better tracking of users across devices and sessions. Documentation: https://support.google.com/analytics/answer/9213390?hl=en