We are in the final process of evaluating zoho subscriptions and plan to write our own customer portal where each of our customers can log into our site and view all their zoho subscriptions, invoices, next invoice amount etc...  Because Zoho Subscriptions only allows up to 10 auth tokens, we planned on using one token for all of our customers and just filter the API data by a specific customer id.  

Is it possible to make API calls like list subscriptions, list invoices etc... for a specific customer only?  If so, does anyone know where the documentation is.  I've looked over the API docs but couldn't find anything.