feat(cloud): handle cancelled subscriptions (#313)

* feat(cloud): handle cancelled subscriptions

* chore: refactor auth

packages/auth/src/utils.ts

@@ -0,0 +1,49 @@
+import type { Subscription } from "@better-auth/stripe";
+import type Stripe from "stripe";
+
+import type { dbClient } from "@kan/db/client";
+import * as userRepo from "@kan/db/repository/user.repo";
+import { notificationClient } from "@kan/email";
+import { createEmailUnsubscribeLink } from "@kan/shared";
+
+export async function downloadImage(url: string): Promise<Buffer> {
+  const response = await fetch(url);
+  if (!response.ok) {
+    throw new Error(`Failed to download image: ${response.statusText}`);
+  }
+  return Buffer.from(await response.arrayBuffer());
+}
+
+export async function triggerWorkflow(
+  db: dbClient,
+  workflowId: string,
+  subscription: Subscription,
+  cancellationDetails?: Stripe.Subscription.CancellationDetails | null,
+) {
+  try {
+    if (!subscription.stripeCustomerId || !notificationClient) return;
+
+    const user = await userRepo.getByStripeCustomerId(
+      db,
+      subscription.stripeCustomerId,
+    );
+
+    if (!user || !notificationClient) return;
+
+    const unsubscribeUrl = await createEmailUnsubscribeLink(user.id);
+
+    await notificationClient.trigger({
+      to: {
+        subscriberId: user.id,
+      },
+      payload: {
+        ...subscription,
+        cancellationDetails,
+        emailUnsubscribeUrl: unsubscribeUrl,
+      },
+      workflowId,
+    });
+  } catch (error) {
+    console.error("Error triggering workflow", error);
+  }
+}