eject plugins fra HPM for å redusere støy

- ikke log error for nettverksissues
- fjerner query delen av requesten i loggene
- legger til en ny metrikk for proxy_status

e.g.
```
proxy_events_total{target: "foo.com", proxystatus="null",status="504",errcode="ENOTFOUND"} 2
```

server/server.js

@@ -1,7 +1,12 @@
 import path from 'path';
 import express from 'express';
 import Mustache from 'mustache';
-import httpProxyMiddleware, { responseInterceptor } from 'http-proxy-middleware';
+import httpProxyMiddleware, {
+    debugProxyErrorsPlugin,
+    errorResponsePlugin,
+    proxyEventsPlugin,
+    responseInterceptor,
+} from 'http-proxy-middleware';
 import { createHttpTerminator } from 'http-terminator';
 import Prometheus from 'prom-client';
 import { createLogger, format, transports } from 'winston';
@@ -28,6 +33,11 @@ const log_events_counter = new Prometheus.Counter({
     help: 'Antall log events fordelt på level',
     labelNames: ['level'],
 });
+const proxy_events_counter = new Prometheus.Counter({
+    name: 'proxy_events_total',
+    help: 'Antall proxy events',
+    labelNames: ['target', 'proxystatus', 'status', 'errcode'],
+});
 
 const maskFormat = format((info) => ({
     ...info,
@@ -55,6 +65,61 @@ const log = new Proxy(
     }
 );
 
+// copy with mods from http-proxy-middleware https://github.com/chimurai/http-proxy-middleware/blob/master/src/plugins/default/logger-plugin.ts
+const loggerPlugin = (proxyServer, options) => {
+    proxyServer.on('error', (err, req, res, target) => {
+        const hostname = req?.headers?.host;
+        // target is undefined when websocket errors
+        const errReference = 'https://nodejs.org/api/errors.html#errors_common_system_errors'; // link to Node Common Systems Errors page
+        proxy_events_counter.inc({
+            target: target.host,
+            proxystatus: null,
+            status: res.statusCode,
+            errcode: err.code || 'unknown',
+        });
+        const level =
+            /HPE_INVALID/.test(err.code) ||
+            ['ECONNRESET', 'ENOTFOUND', 'ECONNREFUSED', 'ETIMEDOUT'].includes(err.code)
+                ? 'warn'
+                : 'error';
+        log.log(
+            level,
+            '[HPM] Error occurred while proxying request %s to %s [%s] (%s)',
+            `${hostname}${req?.host}${req?.path}`,
+            `${target?.href}`,
+            err.code || err,
+            errReference
+        );
+    });
+
+    proxyServer.on('proxyRes', (proxyRes, req, res) => {
+        const originalUrl = req.originalUrl ?? `${req.baseUrl || ''}${req.url}`;
+        const pathUpToSearch = proxyRes.req.path.replace(/\?.*$/, '');
+        const exchange = `[HPM] ${req.method} ${originalUrl} -> ${proxyRes.req.protocol}//${proxyRes.req.host}${pathUpToSearch} [${proxyRes.statusCode}]`;
+        proxy_events_counter.inc({
+            target: proxyRes.req.host,
+            proxystatus: proxyRes.statusCode,
+            status: res.statusCode,
+            errcode: null,
+        });
+        log.info(exchange);
+    });
+
+    /**
+     * When client opens WebSocket connection
+     */
+    proxyServer.on('open', (socket) => {
+        log.info('[HPM] Client connected: %o', socket.address());
+    });
+
+    /**
+     * When client closes WebSocket connection
+     */
+    proxyServer.on('close', (req, proxySocket, proxyHead) => {
+        log.info('[HPM] Client disconnected: %o', proxySocket.address());
+    });
+};
+
 log.info(`Frackend startup: ${JSON.stringify({ NAIS_CLUSTER_NAME, MILJO, GIT_COMMIT })}`);
 
 let BUILD_PATH = path.join(process.cwd(), '../build');
@@ -132,6 +197,8 @@ const main = async () => {
             secure: true,
             xfwd: true,
             changeOrigin: true,
+            ejectPlugins: true,
+            plugins: [debugProxyErrorsPlugin, errorResponsePlugin, loggerPlugin, proxyEventsPlugin],
         };
         app.use(
             '/min-side-arbeidsgiver/tiltaksgjennomforing-api',