Fix system proxy endpoint forwarding query params (#2245)

DEFRA/water-abstraction-team#54
https://eaflood.atlassian.net/browse/WATER-3787

In a previous change we [Create system proxy endpoint](#2229). We need this to be able to send requests to the [water-abstraction-system](https://github.com/DEFRA/water-abstraction-system) when using our AWS environments.

That all seemed to work until we changed an endpoint in **water-abstraction-system** to require a query param to be passed through. Our proxy isn't doing this so now **water-abstraction-system** errors because of the missing param.

This change fixes the issue by switching to [h2o2](https://github.com/hapijs/h2o2) which "adds proxying functionality to a hapi server."

When we first implemented our proxy, we did it ourselves. The issue with the query params would require us to continue to expand that functionality, and we haven't even got to `POST`, `PUT` and `DELETE` requests yet!

So, before we went down that route we investigated what options were available and found this plugin. The documentation and current examples all direct you to use this if you need Hapi to act like a reverse/pass-through proxy server.

We should have done this from the outset, but we've at least stopped before we expanded our own functionality further.

Author: Cruikshanks

package-lock.json

@@ -34,6 +34,7 @@
     "@hapi/boom": "^9.1.4",
     "@hapi/catbox-redis": "^6.0.2",
     "@hapi/good": "^9.0.1",
+    "@hapi/h2o2": "^10.0.0",
     "@hapi/hapi": "^20.2.1",
     "@hapi/hoek": "^9.2.1",
     "@hapi/inert": "^6.0.5",

package.json

@@ -5,6 +5,7 @@ const { createPlugins, createCache } = require('./server-common')
 
 // -------------- Require vendor code -----------------
 const Hapi = require('@hapi/hapi')
+const H2o2 = require('@hapi/h2o2')
 
 // -------------- Require project code -----------------
 const config = require('./src/internal/config')
@@ -103,6 +104,9 @@ async function start () {
     // Auth plugin
     await server.register(authPlugin)
 
+    // Proxy plugin
+    await server.register(H2o2)
+
     server.route(routes)
 
     await server.start()

server-internal.js

@@ -1,12 +1,32 @@
 'use strict'
 
-const controller = require('./controller')
+const config = require('../../config')
+
+const systemUrl = new URL(config.services.system)
+const proxyDefaults = {
+  timeout: 15000, // 15 seconds - default is 3 minutes
+  // Forwards the headers from the client to the upstream service. This is needed for system to receive things like the
+  // `accept:` header, which indicates what MIME type is requested.
+  passThrough: true,
+  // Sets the 'X-Forwarded-For', 'X-Forwarded-Port', 'X-Forwarded-Proto', 'X-Forwarded-Host' headers. 'X-Forwarded-For',
+  // for example, is the standard header for identifying the originating IP address of a client connecting to a web
+  // server through a proxy server. As such, it is often used in security and authentication checks.
+  xforward: true
+}
 
 const routes = [
   {
     method: 'GET',
+    // This will match all path segments after /system. Note in our proxy URI we refer to this only as {tail}. The path
+    // param hapi provides will contain all the segments, for example, request.params.tail === '/test/supplementary'.
+    // We need to refer to it in the same way we access it on the request object.
     path: '/system/{tail*}',
-    handler: controller.getSystemProxy,
+    handler: {
+      proxy: {
+        uri: `${systemUrl.protocol}//${systemUrl.hostname}:${systemUrl.port}/{tail}{query}`,
+        ...proxyDefaults
+      }
+    },
     config: {
       auth: false,
       description: 'Proxies requests to the Water Abstraction System'
@@ -15,7 +35,12 @@ const routes = [
   {
     method: 'GET',
     path: '/assets/all.js',
-    handler: controller.getSystemJsProxy,
+    handler: {
+      proxy: {
+        uri: `${systemUrl.protocol}//${systemUrl.hostname}:${systemUrl.port}/assets/all.js`,
+        ...proxyDefaults
+      }
+    },
     config: {
       auth: false,
       description: 'Proxies JS asset requests to the Water Abstraction System'
@@ -24,7 +49,12 @@ const routes = [
   {
     method: 'GET',
     path: '/assets/stylesheets/application.css',
-    handler: controller.getSystemCssProxy,
+    handler: {
+      proxy: {
+        uri: `${systemUrl.protocol}//${systemUrl.hostname}:${systemUrl.port}/assets/stylesheets/application.css`,
+        ...proxyDefaults
+      }
+    },
     config: {
       auth: false,
       description: 'Proxies CSS asset requests to the Water Abstraction System'