Cleanup shop & add specification

Also reverted v2 change: `GET /shop/v2/` -> `GET /shop/`
Cleaned up `POST /shop/item/buy/` with `{ itemName: "Jacket" }` to
`{ name: "Jacket", ..all additional item properties }`

Author: Timothy-Gonzalez

src/database/models.ts

@@ -8,7 +8,7 @@ import { MentorOfficeHours } from "./mentor-db";
 import { Event, EventAttendance, EventFollowers } from "./event-db";
 import { NewsletterSubscription } from "./newsletter-db";
 import { RegistrationApplication } from "./registration-db";
-import { ShopItem } from "./shop-db";
+import { ShopItem } from "../services/shop/shop-schemas";
 import { UserAttendance, UserInfo } from "../services/user/user-schemas";
 import { AnyParamConstructor, IModelOptions } from "@typegoose/typegoose/lib/types";
 import { StaffShift } from "../services/staff/staff-schemas";