Just wondering if there's an add-on or a way to allow each customer to have api access?
Similar to the shopify one: https://shopify.dev/docs/storefront-api
there is no general credential mechanism in cs-cart. Admin type users can have API keys. I suppose you could create an admin account and then use Privileges to hone down access to what your want to allow. Maybe if you could describe the workflow of what you want to achieve, we might be better able to advise you a solution.