[pino-http] Add err to ServerResponse (#38426)

* [pino-http] Add err to ServerResponse

* err is optional on ServerResponse

types/pino-http/index.d.ts

@@ -39,4 +39,7 @@ declare module 'http' {
     interface IncomingMessage {
         log: Logger;
     }
+    interface ServerResponse {
+        err?: Error;
+    }
 }

types/pino-http/pino-http-tests.ts

@@ -9,6 +9,7 @@ const httpLogger = pinoHttp();
 function handle(req: http.IncomingMessage, res: http.ServerResponse) {
   httpLogger(req, res);
   req.log.info('something else');
+  const err: Error | undefined = res.err;
 }
 
 pinoHttp({ logger });