Test the checkout code; publish images only for releases (#5)

- src/checkout/ (PayPal order request, pricing, VAT) and src/logging/format.ts
  hold the checkout's pure code, moved out of PayPalApi, the product service
  and config without a behaviour change.
- npm test runs node:test on the TypeScript sources (type stripping), with no
  dependencies: 21 tests, 13 pin today's output, 8 describe the correct
  behaviour for the known defects of libretech/mp#67
  and are marked todo.
- CI: the tests run in the image's base (node:22.14.0-alpine) for every pull
  request, push to main and release tag. The image is built for pull requests
  and built and published only for v* tags; main no longer publishes :main
  and :sha-* images.

Refs libretech/mp#71

Co-authored-by: Michael Czechowski <mail@librete.ch>

src/services/PayPalApi.ts

@@ -1,16 +1,7 @@
-import {
-	Client,
-	Environment,
-	LogLevel,
-	OrdersController,
-	CheckoutPaymentIntent,
-	OrderRequest,
-	OrderApplicationContextShippingPreference,
-	Item
-} from "@paypal/paypal-server-sdk";
-import { paypalClientId, paypalClientSecret, paypalEnvironment, vatIncludedDecimal, vatDecimalExcluded } from "../../config/constants";
+import { Client, Environment, LogLevel, OrdersController, OrderRequest } from "@paypal/paypal-server-sdk";
+import { paypalClientId, paypalClientSecret, paypalEnvironment } from "../../config/constants";
 import { Order } from "../../types";
-import { calculateTotalProductPrice } from "../api/product/services/product";
+import { buildPayPalOrderItems, buildPayPalOrderRequest } from "../checkout/paypal-order";
 
 class PayPalApi {
 	private readonly client: Client;
@@ -34,76 +25,12 @@ class PayPalApi {
 	}
 
 	async createSessionOrThrow(returnUrl: string, order: Order) {
-		if (!order.total) throw new Error("Cart is empty or has no total");
-
-		const items = order.cart.map((item) => {
-			const totalProductPrice = calculateTotalProductPrice(item.product);
-			const amount = totalProductPrice / vatIncludedDecimal;
-			const tax = totalProductPrice - amount;
-
-			return {
-				name: item.product.name,
-				unitAmount: {
-					currencyCode: "EUR",
-					value: amount.toFixed(2)
-				},
-				tax: {
-					currencyCode: "EUR",
-					value: tax.toFixed(2)
-				},
-				quantity: item.count.toString()
-			} as Item;
-		});
+		// Outside the try block, so these throws are not logged here. The items are computed but not sent.
+		buildPayPalOrderItems(order);
 
 		try {
 			const collect = {
-				body: {
-					intent: CheckoutPaymentIntent.Capture,
-					purchaseUnits: [
-						{
-							// items,
-							referenceId: order.uuid,
-							amount: {
-								currencyCode: "EUR",
-								value: order.total.toFixed(2),
-								breakdown: {
-									itemTotal: {
-										currencyCode: "EUR",
-										value: (Math.round((order.subtotal / vatIncludedDecimal) * 100) / 100).toFixed(2)
-									},
-									taxTotal: {
-										currencyCode: "EUR",
-										value: order.VAT.toFixed(2)
-									},
-									shipping: order.delivery
-										? {
-												currencyCode: "EUR",
-												value: order.delivery.price.toFixed(2)
-											}
-										: undefined
-								}
-							},
-							shipping: {
-								name: {
-									fullName: order.deliveryAddress.split("\n")[0]
-								},
-								address: {
-									addressLine1: order.deliveryAddress.split("\n")[1],
-									postalCode: order.deliveryAddress.split("\n")[2].slice(0, 5),
-									adminArea2: order.deliveryAddress.split("\n")[2].slice(6),
-									countryCode: "DE"
-								}
-							},
-							customId: order.uuid,
-							invoiceId: order.invoiceNumber
-						}
-					],
-					applicationContext: {
-						returnUrl: returnUrl,
-						cancelUrl: returnUrl,
-						shippingPreference: OrderApplicationContextShippingPreference.SetProvidedAddress
-					}
-				} as OrderRequest,
+				body: buildPayPalOrderRequest(returnUrl, order) as OrderRequest,
 				prefer: "return=minimal"
 			};