We are using Odoo Online and want to integrate it with our custom web application.

Use Case:

We want to sell a software package via the Odoo website/shop to users of our own web app. In our web app, users will click a "Buy" button, which redirects them to the corresponding product page on our Odoo webshop.

We want to track which user in our system made the purchase, so our idea is to pass the internal UserID from our app as a URL parameter (e.g., ?uid=12345) when redirecting to Odoo.

Our requirements:

• The UserID should be passed in the URL (done from our web app).
• The UserID should be stored somewhere in the Sales Order (ideally in a custom field or notes).
• We are using Odoo Online (not Odoo.sh or self-hosted), so we are limited in terms of custom code or modules.

Questions:

1. Is there a way in Odoo Online to capture a URL parameter and store it in the Sales Order?
2. Is there a workaround (e.g., using UTM parameters, custom questions during checkout, or modifying the lead source)?

Any help, tips, or workarounds are highly appreciated!

Thanks in advance!