fix(express-wrapper): dont override status code in req

In the event of an error in handleRequest,
only set the status code on the request if it hasn't already been set.

Overriding the status code in the event of an error results in
incorrect reporting of the error status code using plugins such
as prom-bundle to generate metrics.

Author: jonball4

packages/express-wrapper/src/request.ts

@@ -131,7 +131,10 @@ export const handleRequest = (
         const response = await serviceFn(handlerParams);
         responseEncoder(httpRoute, response)(req, res, next);
       } catch (err) {
-        res.status(500).end();
+        if (!res.statusCode) {
+          res.status(500);
+        }
+        res.end();
         next();
         return;
       }