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

software/backend/models/product.model.ts

@@ -0,0 +1,30 @@
+import { Table, Column, Model, ForeignKey, BelongsTo, BelongsToMany } from 'sequelize-typescript';
+import { Category } from './category.model';
+import { OrderedItem } from './orderedItem.model';
+import { Order } from './order.model';
+
+@Table
+export class Product extends Model {
+  @Column
+  brand: string
+  
+  @Column
+  name: string
+
+  @Column
+  @ForeignKey(() => Category)
+  categoryId: number
+
+  @Column
+  price: number
+
+  @Column
+  discount: number
+  
+  // Relations
+  @BelongsTo(() => Category)
+  category: Category
+
+  @BelongsToMany(() => Order,() => OrderedItem)
+  orderedItem: OrderedItem
+}