Fix db relations, add sample data, show categories in frontend menu

software/backend/routes/product.routes.ts

@@ -0,0 +1,12 @@
+import { Router, Request, Response, NextFunction } from "express";
+import { Product } from "../models/product.model";
+
+export const product = Router()
+
+product.get("/", (req: Request, res: Response, next: NextFunction)=> {
+  Product.findAll()
+    .then(products => {
+      res.json(products)
+    })
+    .catch(next)
+})