Flatten Vector-override components (#28346)

* Flatten Vector-override components

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Iterate

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Iterate

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Improve coverage

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Iterate

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Iterate

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Ie

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* delint

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

---------

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

test/unit-tests/components/views/auth/AuthPage-test.tsx

@@ -0,0 +1,36 @@
+/*
+Copyright 2024 New Vector Ltd.
+Copyright 2022 The Matrix.org Foundation C.I.C.
+
+SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only
+Please see LICENSE files in the repository root for full details.
+*/
+
+import * as React from "react";
+import { render } from "jest-matrix-react";
+
+import AuthPage from "../../../../../src/components/views/auth/AuthPage";
+import { setupLanguageMock } from "../../../../setup/setupLanguage";
+import SdkConfig from "../../../../../src/SdkConfig.ts";
+
+describe("<AuthPage />", () => {
+    beforeEach(() => {
+        setupLanguageMock();
+        SdkConfig.reset();
+        // @ts-ignore private access
+        AuthPage.welcomeBackgroundUrl = undefined;
+    });
+
+    it("should match snapshot", () => {
+        const { asFragment } = render(<AuthPage />);
+        expect(asFragment()).toMatchSnapshot();
+    });
+
+    it("should use configured background url", () => {
+        SdkConfig.add({ branding: { welcome_background_url: ["https://example.com/image.png"] } });
+        const { container } = render(<AuthPage />);
+        expect(container.querySelector(".mx_AuthPage")).toHaveStyle({
+            background: "center/cover fixed url(https://example.com/image.png)",
+        });
+    });
+});