Harden msgraph webhook auth requirements (#30169)

gateway/platforms/msgraph_webhook.py

@@ -133,6 +133,12 @@ class MSGraphWebhookAdapter(BasePlatformAdapter):
         self._notification_scheduler = scheduler
 
     async def connect(self) -> bool:
+        if self._client_state is None:
+            logger.error(
+                "[msgraph_webhook] Refusing to start without extra.client_state configured"
+            )
+            return False
+
         app = web.Application()
         app.router.add_get(self._health_path, self._handle_health)
         app.router.add_get(self._webhook_path, self._handle_validation)
@@ -310,7 +316,7 @@ class MSGraphWebhookAdapter(BasePlatformAdapter):
         """
         expected = self._client_state
         if expected is None:
-            return True
+            return False
         provided = self._string_or_none(notification.get("clientState"))
         if provided is None:
             return False