Node.Js Programmer - Server Side

We are planning to add Promo Code option to our subscription module. The existing code base is written in Node.js and the existing API is well documented. Technical requirements 1) Design and Write an API to a) Generate a promo code b) Validate a promo code c) Give a expiry to promo code d) Assign a susbscription duration to a promo cde 2) Create a data base table and add to the existing user table to record the promo codes The candidate should be able to code, be able to write the API and document it for future references.