Checkout: forward only the checkout fields, show clear errors, fix the contact form (#16)

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

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;
+		}
+	}
+}