fix(backend): redact retryable MAX storage failures

Refs #82

app/api/max_notifications.py

@@ -10,6 +10,7 @@ from fastapi import APIRouter, Depends, HTTPException, Request
 from fastapi.security import HTTPAuthorizationCredentials, HTTPBearer
 from pydantic import BaseModel, ConfigDict
 from sqlalchemy import select
+from sqlalchemy.exc import SQLAlchemyError
 
 from app.config import get_settings
 from app.core import clock
@@ -106,5 +107,9 @@ async def webhook(request: Request) -> dict[str, bool]:
         raise HTTPException(422, "event must be an object")
     from app.channels.max_bot import handle_update
 
+    try:
         await handle_update(event)
+    except SQLAlchemyError:
+        # Let MAX retry; do not log DB exception parameters containing identity data.
+        raise HTTPException(503, "notification storage unavailable") from None
     return {"success": True}

tests/test_api_max.py

@@ -1,9 +1,13 @@
 """MAX endpoints authenticate before reading bindings or accepting events."""
 
+import sys
+from types import SimpleNamespace
+from unittest.mock import AsyncMock
 from urllib.parse import parse_qs, urlsplit
 
 import pytest
 from httpx import ASGITransport, AsyncClient
+from sqlalchemy.exc import OperationalError
 
 from app.config import get_settings
 from app.core import clock
@@ -90,3 +94,10 @@ async def test_webhook_secret_checked_before_body_or_adapter(client):
     assert (await client.post(HOOK, headers=headers, content="not-json")).status_code == 400
     assert (await client.post(HOOK, headers=headers, json=[])).status_code == 422
     assert (await client.post(HOOK, headers=headers, content=" " * 65537)).status_code == 413
+
+
+async def test_webhook_storage_failure_is_retryable_without_identity_details(client, monkeypatch):
+    handler = AsyncMock(side_effect=OperationalError("private SQL", {"token": TOKEN}, Exception("private")))
+    monkeypatch.setitem(sys.modules, "app.channels.max_bot", SimpleNamespace(handle_update=handler))
+    response = await client.post(HOOK, headers={"X-Max-Bot-Api-Secret": SECRET}, json={})
+    assert response.status_code == 503 and TOKEN not in response.text and "private" not in response.text