I’ve installed medusa js using the create-medusa-app command and it successfully created 2 folders medusa & medusa-storefront. In medusa-storefront there is next js source code of every module but in the medusa folder there are no routes and controller functions for customizing the backend. I want a simple add to cart function but it is only in the medusa-storefront(nextJS) and it’s using browser storage for adding products to the cart and not in the backend. As of now I want to store this product in my DB using backend and there are no routes and controllers for this. How do I setup my backend ?

I tried searching it in the src folder but in the routes.ts file it’s empty. I’m looking for the atleast one functionality like add to cart so that I may understand it and create further functionalities.
Below is the only code in the routes.ts file:-
` import { MedusaRequest, MedusaResponse } from “@medusajs/medusa”;

  export async function GET(
  req: MedusaRequest,
  res: MedusaResponse
): Promise<void> {
  res.sendStatus(200);
}`