feat(orders): pass the CMS's status and safe error fields to the browser

The order routes (get, put, add-product, remove-product, checkout, capture)
call forwardToCms, which throws a CMS error on as
createError({ statusCode, statusMessage, data: { message, errors?, missing? } }),
built by the pure shopErrorFromCms (server/utils/cmsError.ts).

Before, the FetchError was thrown on as it was: the browser got the CMS's
status, but Nitro treated it as unhandled, answered "Server Error" without
data and logged every CMS 4xx as [unhandled]. Now the browser also gets the
CMS's message, the errors of a rejected update and the fields a checkout
misses, and no other field. A status that is the shop's own fault (401, 403,
...) is answered 500, a CMS that does not answer 503; 5xx are logged without
the query and the order uuid.

npm test runs tests/unit with Node's type stripping and no dependencies, as
in libreshop/cms. nuxt.config keeps tests/ out of the app's type check.

Refs libretech/mp#71

tests/unit/support/register.mjs

@@ -0,0 +1,6 @@
+// Loaded by `npm test` through `node --import`. Node runs the .ts sources directly (type stripping), but unlike Vite and Nitro it does
+// not resolve extensionless relative imports such as `import { … } from "./cmsError"` in a server/utils module.
+// The hook below retries such an import from a .ts file with ".ts" appended. Test files import sources with explicit .ts paths.
+import { register } from "node:module";
+
+register("./resolve-ts.mjs", import.meta.url);

tests/unit/support/resolve-ts.mjs

@@ -0,0 +1,14 @@
+// Module resolve hook, registered by ./register.mjs: `./cmsError` imported from a .ts file resolves to `./cmsError.ts`.
+export async function resolve(specifier, context, nextResolve) {
+	try {
+		return await nextResolve(specifier, context);
+	} catch (error) {
+		const relative = specifier.startsWith("./") || specifier.startsWith("../");
+		if (error?.code !== "ERR_MODULE_NOT_FOUND" || !relative || !context.parentURL?.endsWith(".ts")) throw error;
+		try {
+			return await nextResolve(`${specifier}.ts`, context);
+		} catch {
+			throw error;
+		}
+	}
+}