rename folder and actually sanity check

src/core/middleware.ts

@@ -0,0 +1,26 @@
+import { Request, Response } from 'express';
+import responseTime = require('response-time');
+import {
+	endpointResponseTimeHistogram,
+	responseStatusCounter,
+} from './metrics';
+
+export const handleResponseTime = responseTime(
+	(req: Request, res: Response, time: number) => {
+		const endpoint = req.path;
+
+		if (endpoint === '/health' || req.url === '/') {
+			return;
+		}
+
+		responseStatusCounter.add(1, {
+			endpoint,
+			status: res.statusCode,
+		});
+
+		const responseTimeMs = time;
+		endpointResponseTimeHistogram.record(responseTimeMs, {
+			endpoint,
+		});
+	}
+);