[Backport 7.x] Added proxy support (#1276)

Co-authored-by: Tomas Della Vedova <delvedor@users.noreply.github.com>

test/utils/buildProxy.js

@@ -0,0 +1,60 @@
+// Licensed to Elasticsearch B.V under one or more agreements.
+// Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information
+
+'use strict'
+
+const proxy = require('proxy')
+const { readFileSync } = require('fs')
+const { join } = require('path')
+const http = require('http')
+const https = require('https')
+
+const ssl = {
+  key: readFileSync(join(__dirname, '..', 'fixtures', 'https.key')),
+  cert: readFileSync(join(__dirname, '..', 'fixtures', 'https.cert'))
+}
+
+function createProxy () {
+  return new Promise((resolve, reject) => {
+    const server = proxy(http.createServer())
+    server.listen(0, '127.0.0.1', () => {
+      resolve(server)
+    })
+  })
+}
+
+function createSecureProxy () {
+  return new Promise((resolve, reject) => {
+    const server = proxy(https.createServer(ssl))
+    server.listen(0, '127.0.0.1', () => {
+      resolve(server)
+    })
+  })
+}
+
+function createServer (handler, callback) {
+  return new Promise((resolve, reject) => {
+    const server = http.createServer()
+    server.listen(0, '127.0.0.1', () => {
+      resolve(server)
+    })
+  })
+}
+
+function createSecureServer (handler, callback) {
+  return new Promise((resolve, reject) => {
+    const server = https.createServer(ssl)
+    server.listen(0, '127.0.0.1', () => {
+      resolve(server)
+    })
+  })
+}
+
+module.exports = {
+  ssl,
+  createProxy,
+  createSecureProxy,
+  createServer,
+  createSecureServer
+}