feat(e2e): add support running behind proxy (#5348)

* docs: update maintaining

* chore(e2e): add maxFailures to playwright

* fix(ci): skip submodule in e2e job

We don't need the submodules for the e2e job. This will speed up the
checkout step.

* feat(ci): add test-e2e-proxy job

This adds a new job to CI to run our tests behind Caddy and simulate
code-server running against a reverse-proxy.

* refactor: make e2e work with reverse proxy

This refactors the e2e test in a couple ways:
- remove setting cookie in localStorage (instead we pass --auth none)
- refactor address() method to account for reverse proxy logic

* Update test/e2e/models/CodeServer.ts

* Update test/playwright.config.ts

* Update test/utils/constants.ts

Co-authored-by: Asher <ash@coder.com>

* Update test/utils/helpers.ts

Co-authored-by: Asher <ash@coder.com>

Co-authored-by: Asher <ash@coder.com>

test/e2e/extensions.test.ts

@@ -1,23 +1,36 @@
 import * as path from "path"
-import { describe, test } from "./baseFixture"
+import { test as base } from "@playwright/test"
+import { describe, test, expect } from "./baseFixture"
+import { getMaybeProxiedCodeServer } from "../utils/helpers"
 
 function runTestExtensionTests() {
   // This will only work if the test extension is loaded into code-server.
   test("should have access to VSCODE_PROXY_URI", async ({ codeServerPage }) => {
-    const address = await codeServerPage.address()
+    const address = await getMaybeProxiedCodeServer(codeServerPage)
 
     await codeServerPage.executeCommandViaMenus("code-server: Get proxy URI")
 
-    await codeServerPage.page.waitForSelector(`text=${address}/proxy/{{port}}`)
+    const text = await codeServerPage.page.locator(".notification-list-item-message").textContent()
+    // Remove end slash in address
+    const normalizedAddress = address.replace(/\/+$/, "")
+    expect(text).toBe(`${normalizedAddress}/proxy/{{port}}`)
   })
 }
 
 const flags = ["--extensions-dir", path.join(__dirname, "./extensions")]
 
-describe("Extensions", true, flags, {}, () => {
+describe("Extensions", flags, {}, () => {
   runTestExtensionTests()
 })
 
-describe("Extensions with --cert", true, [...flags, "--cert"], {}, () => {
-  runTestExtensionTests()
-})
+if (process.env.USE_PROXY !== "1") {
+  describe("Extensions with --cert", [...flags, "--cert"], {}, () => {
+    runTestExtensionTests()
+  })
+} else {
+  base.describe("Extensions with --cert", () => {
+    base.skip("skipped because USE_PROXY is set", () => {
+      // Playwright will not show this without a function.
+    })
+  })
+}