Add authkey header for requests to the backend (#256)

With this PR, Electron will generate a new authorization key that the Go
backend will look for in any incoming requests. The Electron backend
will inject this header with all requests to the backend to ensure no
additional work is required on the frontend.

This also adds a `fetchutil` abstraction that will use the Electron
`net` module when calls are made from the Electron backend to the Go
backend. When using the `node:fetch` module, Electron can't inject
headers to requests. The Electron `net` module is also faster than the
Node module.

This also breaks out platform functions in emain into their own file so
other emain modules can import them.

frontend/app/store/global.ts

@@ -10,6 +10,7 @@ import {
     newLayoutNode,
 } from "@/layout/index";
 import { getWebServerEndpoint, getWSServerEndpoint } from "@/util/endpoints";
+import { fetch } from "@/util/fetchutil";
 import { produce } from "immer";
 import * as jotai from "jotai";
 import * as rxjs from "rxjs";

frontend/app/store/wos.ts

@@ -5,6 +5,7 @@
 
 import { sendRpcCommand } from "@/app/store/wshrpc";
 import { getWebServerEndpoint } from "@/util/endpoints";
+import { fetch } from "@/util/fetchutil";
 import * as jotai from "jotai";
 import * as React from "react";
 import { atoms, globalStore } from "./global";

frontend/types/custom.d.ts

@@ -52,6 +52,7 @@ declare global {
     };
 
     type ElectronApi = {
+        getAuthKey(): string;
         getIsDev(): boolean;
         getCursorPoint: () => Electron.Point;
 

frontend/util/fetchutil.ts

@@ -0,0 +1,20 @@
+// Copyright 2024, Command Line Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+// Utility to abstract the fetch function so the Electron net module can be used when available.
+
+let net: Electron.Net;
+
+try {
+    import("electron").then(({ net: electronNet }) => (net = electronNet));
+} catch (e) {
+    // do nothing
+}
+
+export function fetch(input: string | GlobalRequest | URL, init?: RequestInit): Promise<Response> {
+    if (net) {
+        return net.fetch(input.toString(), init);
+    } else {
+        return globalThis.fetch(input, init);
+    }
+}