Generate a short-lived Stripe Billing Portal session for an organization admin.
This portal link allows the admin to manage billing-related tasks securely within Stripe’s hosted UI.
The returned url is a temporary, single-use HTTPS link to Stripe’s billing portal, e.g.:
https://billing.stripe.com/p/session/test_YWNjdF8xUjVENkJDdnlkaXZnY21CLF9UNzRYcVA3eDZ4eEExS0I2ZDNLUmhVUHVXWGZSd2xC01003ZjV6GWq
⚠️ Security note: This URL is short-lived and should only be shown to the authenticated admin requesting it. Do not persist or reuse it in your own database.