BETTERZON-38: Added all currently required models with required service classes and routers

Backend/src/models/prices/price.interface.ts

@@ -0,0 +1,7 @@
+export interface Price {
+    price_id: number;
+    product_id: number;
+    vendor_id: number;
+    price_in_cents: number;
+    timestamp: Date;
+}