[LEBV-356] Add tracker to QR code

🎯 Summary

Add a tracker of some sort so that we can track how many users accessed the customer onboarding on phone after scanning the QR code, like https://videoident-customer-onboarding.lebara.com/?utm_source=lebara&utm_medium=devicechange&utm_campaign=regjourneystep1

🧪 How to test

Repeat the steps documented here : !57 (merged) but in the branch 'LEBV-356-qr_trackable'

🧠 Considerations

Special considerations

🧐 Checklist

Changes work in Google Chrome
Changes work in Safari
UI is responsive