Cross domain tracking from Source > Wordpress (A.dk) > Webapp (app.B.com) > Payment (Stripe)

Create a cross domain tracking so I can follow the customer's journey all the way from the source to the payment*. Goal: See which source (google ads, youtube, facebooks ads, organic, blog etc...) is converting best into payment, so we can do better conversion rate optimization. 1. Google ads (Adwords, banners, Youtube ads etc.) / Organic search / other sources 2. Wordpress site as frontpage (domain [login to view URL]) 3. Webapp, where signup, login and magic happens (domain [login to view URL]) 4. Stripe* *If possible. And If not possible I want to know why. Sub-tasks: 1. Enable tracking (using Google Tag manager) from source to webapp and if possible payment. 2. Control/correct funnel in google analytics. 3. Make some test (from google adwords + organic) and make a mini report showing it's working (the users can be followed all the way + payment seen in Google analytics match payment in stripe) 4. Small report on what has been done (if code has been added and what to know exactly where and what code). I will provide you with: A. Access to google adwords B. Access to google tag manager C. Access to google analyics D. Access to stripe (under some restriction) Note: the work done must not be affected by updating plugins or themes in Wordpress or updates in the webapp. Here is the google Guide for the part before Stripe: [login to view URL] I am not sure it's possible to follow one customer all the way to Stripe, as it sometimes goes many days before an user upgrade. If it's possible I want it to be done, and if it's not possible, I want to now exactly why it's not possible.