fix: add .catch() to fire-and-forget setMeta and track error fingerprints

Prevent unhandled promise rejection crash when Redis is down during
Pub/Sub error handling. Track error fingerprint so changed error types
are re-logged instead of silently suppressed. Add clarifying comments
and align test helper with constructor-initialized properties.

Author: andris9

lib/oauth/pubsub/google.js

@@ -18,8 +18,10 @@ class PubSubInstance {
         this.stopped = false;
         this.recoveryAttempts = 0;
         this.lastRecoveryAttempt = 0;
+        // Initialize to true so the first successful pull clears any stale
+        // pubSubFlag left in Redis by a previously crashed process
         this._hadPubSubFlag = true;
-        this._loopErrorLogged = false;
+        this._lastLoopError = null;
 
         this.checkSchemaVersions()
             .catch(err => {
@@ -38,21 +40,26 @@ class PubSubInstance {
         }
         this.run()
             .then(() => {
-                this._loopErrorLogged = false;
+                this._lastLoopError = null;
                 this.startLoop();
             })
             .catch(err => {
-                if (!this._loopErrorLogged) {
+                let errKey = [err.message, err.code, err.statusCode].filter(val => val).join('|');
+                if (this._lastLoopError !== errKey) {
                     logger.error({ msg: 'Failed to process subscription loop', app: this.app, err });
-                    this._loopErrorLogged = true;
+                    this._lastLoopError = errKey;
 
                     this._hadPubSubFlag = true;
-                    oauth2Apps.setMeta(this.app, {
-                        pubSubFlag: {
-                            message: `Failed to process subscription loop`,
-                            description: [err.message, err.reason, err.code].filter(val => val).join('; ')
-                        }
-                    });
+                    oauth2Apps
+                        .setMeta(this.app, {
+                            pubSubFlag: {
+                                message: `Failed to process subscription loop`,
+                                description: [err.message, err.reason, err.code].filter(val => val).join('; ')
+                            }
+                        })
+                        .catch(metaErr => {
+                            logger.error({ msg: 'Failed to update pubSubFlag', app: this.app, err: metaErr });
+                        });
                 }
                 setTimeout(() => this.startLoop(), err.retryDelay || 3000);
             });

lib/oauth2-apps.js

@@ -851,6 +851,8 @@ class OAuth2AppsHandler {
         };
     }
 
+    // Note: not atomic (read-modify-write). Concurrent callers use last-write-wins,
+    // which is acceptable for self-correcting informational metadata.
     async setMeta(id, meta) {
         let existingMeta;
         let existingMetaBuf = await this.redis.hgetBuffer(this.getDataKey(), `${id}:meta`);

test/pubsub-recovery-test.js

@@ -238,6 +238,8 @@ function createTestInstance(overrides) {
             stopped: false,
             recoveryAttempts: 0,
             lastRecoveryAttempt: 0,
+            _hadPubSubFlag: true,
+            _lastLoopError: null,
             parent: { getSubscribersKey: () => 'ee:oapp:sub', remove: () => {} },
             appData: { id: 'test-app', pubSubSubscription: 'projects/test/subscriptions/test-sub' },
             client: {