FN-5778: throttle OAuth expiry notifications per provider

Limit repeated oauth-token-expired alerts by enforcing a per-provider minimum notification interval.

- add a 12-hour default min notify interval to OAuthExpiryMonitor and track last notification time by provider
- skip dispatch when a provider was already notified within the configured window, even if expiry timestamps change
- clear per-provider notification timestamps when no OAuth providers are configured
- add regression coverage for 12-hour throttling and changed-expiry throttling behavior
- add a patch changeset for @runfusion/fusion documenting the notification throttle

Files changed:
 .changeset/fn-5778-oauth-notify-throttle.md        |  5 +++
 packages/engine/src/notification/__tests__/oauth-expiry-monitor.test.ts         | 40 ++++++++++++++++++++++
 packages/engine/src/notification/oauth-expiry-monitor.ts       | 15 ++++++++
 3 files changed, 60 insertions(+)

Fusion-Task-Id: FN-5778

Fusion-Task-Lineage: a9741101-e8da-4dae-ac7f-817e564b4f23

packages/engine/src/notification/__tests__/oauth-expiry-monitor.test.ts

@@ -121,6 +121,46 @@ describe("OAuthExpiryMonitor", () => {
     now += 2_000;
     await vi.advanceTimersByTimeAsync(100);
 
+    expect(dispatch).toHaveBeenCalledTimes(1);
+
+    now += 12 * 60 * 60 * 1000;
+    await vi.advanceTimersByTimeAsync(100);
+
+    expect(dispatch).toHaveBeenCalledTimes(2);
+    monitor.stop();
+    vi.useRealTimers();
+  });
+
+  it("throttles changed expiries until min notify interval elapses", async () => {
+    vi.useFakeTimers();
+    let now = Date.now();
+    const authStorage = createAuthStorage({ type: "oauth", expires: now - 1 });
+    const dispatch = vi.fn(async () => undefined);
+
+    const monitor = new OAuthExpiryMonitor({
+      authStorage,
+      notificationService: { dispatch } as any,
+      intervalMs: 100,
+      minNotifyIntervalMs: 1_000,
+      clock: () => now,
+    });
+
+    await monitor.start();
+    expect(dispatch).toHaveBeenCalledTimes(1);
+
+    authStorage.credential = { type: "oauth", expires: now + 10_000 };
+    await vi.advanceTimersByTimeAsync(100);
+
+    now += 500;
+    authStorage.credential = { type: "oauth", expires: now - 1 };
+    await vi.advanceTimersByTimeAsync(100);
+
+    expect(dispatch).toHaveBeenCalledTimes(1);
+
+    now += 500;
+    authStorage.credential = { type: "oauth", expires: now - 2 };
+    await vi.advanceTimersByTimeAsync(100);
+
     expect(dispatch).toHaveBeenCalledTimes(2);
     monitor.stop();
     vi.useRealTimers();

packages/engine/src/notification/oauth-expiry-monitor.ts

@@ -3,6 +3,7 @@ import { schedulerLog } from "../logger.js";
 import type { NotificationService } from "./notification-service.js";
 
 const DEFAULT_INTERVAL_MS = 5 * 60_000;
+const DEFAULT_MIN_NOTIFY_INTERVAL_MS = 12 * 60 * 60 * 1000;
 
 interface OAuthProviderInfo {
   id: string;
@@ -26,19 +27,23 @@ export interface OAuthExpiryMonitorOptions {
   intervalMs?: number;
   clock?: () => number;
   warnBeforeMs?: number;
+  minNotifyIntervalMs?: number;
 }
 
 export class OAuthExpiryMonitor {
   private readonly intervalMs: number;
   private readonly clock: () => number;
   private readonly warnBeforeMs: number;
+  private readonly minNotifyIntervalMs: number;
   private timer: NodeJS.Timeout | null = null;
   private readonly dispatchedExpiryKeys = new Set<string>();
+  private readonly lastNotifiedAt = new Map<string, number>();
 
   constructor(private readonly opts: OAuthExpiryMonitorOptions) {
     this.intervalMs = opts.intervalMs ?? DEFAULT_INTERVAL_MS;
     this.clock = opts.clock ?? Date.now;
     this.warnBeforeMs = opts.warnBeforeMs ?? 0;
+    this.minNotifyIntervalMs = opts.minNotifyIntervalMs ?? DEFAULT_MIN_NOTIFY_INTERVAL_MS;
   }
 
   async start(): Promise<void> {
@@ -68,6 +73,7 @@ export class OAuthExpiryMonitor {
     const providers = this.opts.authStorage.getOAuthProviders?.();
     if (!providers?.length) {
       this.dispatchedExpiryKeys.clear();
+      this.lastNotifiedAt.clear();
       return;
     }
 
@@ -90,6 +96,14 @@ export class OAuthExpiryMonitor {
         continue;
       }
 
+      const previousNotificationAt = this.lastNotifiedAt.get(provider.id);
+      if (
+        typeof previousNotificationAt === "number" &&
+        now - previousNotificationAt < this.minNotifyIntervalMs
+      ) {
+        continue;
+      }
+
       const payload: NotificationPayload = {
         event: "oauth-token-expired",
         metadata: {
@@ -102,6 +116,7 @@ export class OAuthExpiryMonitor {
       try {
         await this.opts.notificationService.dispatch("oauth-token-expired", payload);
         this.dispatchedExpiryKeys.add(expiryKey);
+        this.lastNotifiedAt.set(provider.id, now);
       } catch (error) {
         const message = error instanceof Error ? error.message : String(error);
         schedulerLog.warn(`OAuth expiry notification dispatch failed provider=${provider.id}: ${message}`);