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

software/backend/routes/orderedItem.routes.ts

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