fix(@angular-devkit/build-angular): properly configure headers for media resources and HTML page

Headers were not configured correctly.

Closes #27464

Author: alan-agius4

packages/angular_devkit/build_angular/src/builders/dev-server/tests/options/headers_spec.ts

@@ -0,0 +1,65 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import { executeDevServer } from '../../index';
+import { executeOnceAndFetch } from '../execute-fetch';
+import { describeServeBuilder } from '../jasmine-helpers';
+import { BASE_OPTIONS, DEV_SERVER_BUILDER_INFO } from '../setup';
+
+describeServeBuilder(
+  executeDevServer,
+  DEV_SERVER_BUILDER_INFO,
+  (harness, setupTarget, isViteRun) => {
+    (isViteRun ? describe : xdescribe)('option: "headers"', () => {
+      beforeEach(async () => {
+        setupTarget(harness, {
+          styles: ['src/styles.css'],
+        });
+
+        // Application code is not needed for these tests
+        await harness.writeFile('src/main.ts', '');
+        await harness.writeFile('src/styles.css', '');
+      });
+
+      it('index response headers should include configured header', async () => {
+        harness.useTarget('serve', {
+          ...BASE_OPTIONS,
+          headers: {
+            'x-custom': 'foo',
+          },
+        });
+
+        const { result, response } = await executeOnceAndFetch(harness, '/');
+
+        expect(result?.success).toBeTrue();
+        expect(await response?.headers.get('x-custom')).toBe('foo');
+      });
+
+      it('media resource response headers should include configured header', async () => {
+        await harness.writeFiles({
+          'src/styles.css': `h1 { background: url('./test.svg')}`,
+          'src/test.svg': `<svg xmlns="http://www.w3.org/2000/svg">
+                          <text x="20" y="20" font-size="20" fill="red">Hello World</text>
+                         </svg>`,
+        });
+
+        harness.useTarget('serve', {
+          ...BASE_OPTIONS,
+          headers: {
+            'x-custom': 'foo',
+          },
+        });
+
+        const { result, response } = await executeOnceAndFetch(harness, '/media/test.svg');
+
+        expect(result?.success).toBeTrue();
+        expect(await response?.headers.get('x-custom')).toBe('foo');
+      });
+    });
+  },
+);

packages/angular_devkit/build_angular/src/builders/dev-server/vite-server.ts

@@ -547,6 +547,7 @@ export async function setupServer(
         outputFiles,
         assets,
         ssr,
+        extraHeaders: serverOptions.headers,
         external: externalMetadata.explicit,
         indexHtmlTransformer,
         extensionMiddleware,