refactor(line): extract node webhook handler + shared verification

src/line/webhook-utils.ts

@@ -0,0 +1,15 @@
+import type { WebhookRequestBody } from "@line/bot-sdk";
+
+export function parseLineWebhookBody(rawBody: string): WebhookRequestBody | null {
+  try {
+    return JSON.parse(rawBody) as WebhookRequestBody;
+  } catch {
+    return null;
+  }
+}
+
+export function isLineWebhookVerificationRequest(
+  body: WebhookRequestBody | null | undefined,
+): boolean {
+  return !!body && Array.isArray(body.events) && body.events.length === 0;
+}