I installed Firebase stripe extension. Every time user is created, the extension creates stripeId.
I created buttons to buy subscription plans
<a class="btn btn-primary" href="https://buy.stripe.com/test_5kA8x65CAeF23Cg8ww" role="button">BASIC</a>
<a class="btn btn-primary" href="https://buy.stripe.com/test_7sI00A0igbsQ4Gk7st" role="button">Premium</a>
How to pass user stripeId in link, so Stripe knows which customers buy it?
Now even customer use the same email, Stripe creates new customer.