TNT-46700 Adding documentation and samples for proxy configuration (#53)

* sample for adding a proxy to the node sdk http calls

* Small typo fix

Co-authored-by: Andrei Anischevici <[email protected]>

---------

Co-authored-by: Eric Fichtel <[email protected]>
Co-authored-by: Andrei Anischevici <[email protected]>

Author: 3 people

proxy-configuration/README.md

@@ -0,0 +1,21 @@
+# Proxy Configuration Sample
+
+## Overview
+
+It is possible to configure a proxy for the Node SDK's HTTP requests. This is possible by overriding the `fetch` API used by the SDK during initialization.
+
+This sample contains three different code snippets that demonstrate how to configure the SDK with a proxy, depending on which Node version the SDK runs on:  
+
+- [Node 18.2+](proxy-sample-node-18.js) (`undici.fetch` is the default `fetch`)
+- [Node 16.8+](proxy-sample-node-16.js) (`undici.fetch` needs to be imported)
+- [Node 14+](proxy-sample-node-14.js) (the proxy is configured with `node-fetch`)
+
+The difference in proxy configurations is due to differences in the fetch implementations between Node versions. 
+Starting with Node 18.2, the default implementation of `fetch` switched to `undici.fetch`. 
+However, `unidici.fetch` is only supported in Node 16.8+. Users are welcome to choose their own `fetch` and proxy client configurations. 
+These samples only serve as guidance for those considering adding a proxy to their SDK HTTP calls. 
+
+## Usage
+
+1. `npm start` to start a local proxy server
+2. in a separate window, run `node proxy-sample-node-[version]` to initialize a sample Target Client and make a `getOffers` call with a proxy configured

proxy-configuration/example-proxy-server.js

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+// eslint-disable-next-line import/no-extraneous-dependencies
+const { createProxyServer } = require("@mutagen-d/node-proxy-server");
+
+const port = 8080;
+const server = createProxyServer();
+
+server.on("error", error => {
+  console.log("server error", error);
+});
+
+server.on("connection", conn => {
+  console.log("Successfully connected", conn);
+});
+
+server.listen(port, "0.0.0.0", () =>
+  console.log("proxy-server listening port", port)
+);