Populate Liquid code with client ID/token at installation

[infinityp913]

Hi, I have built an embedded app. At installation, I want to populate a variable in the Liquid code with an ID associated with the merchant (on my app's backend).

I was advised to use the App URL to redirect to a page containing a simple HTML form for the merchant to enter the ID. But, I'm not sure how I can send that ID over to the Liquid code if say, I store that ID in my own database.

A better user experience would be that after installation, the merchant is redirected to my app's website where they can create an account (or login) and then the ID generated is somehow passed over to the Liquid code which can then correctly configure the embedded app. How would you suggest I go about implementing this flow?