feat: add агегку events

src/common/decorators/api-safe-error-response.decorator.ts

@@ -38,6 +38,7 @@ export function ApiProblemResponses(): MethodDecorator & ClassDecorator {
     problemResponse(400, 'Invalid request'),
     problemResponse(401, 'Authentication required'),
     problemResponse(404, 'Resource not found'),
+    problemResponse(503, 'Upstream service unavailable'),
     problemResponse(500, 'Internal server error'),
   );
 }