[Serve] Produtionize Starlette Middlewares (#10529)

doc/source/serve/advanced.rst

@@ -316,3 +316,31 @@ To call a method via Python, do the following:
 
     handle = serve.get_handle("backend_name")
     handle.options(method_name="other_method").remote(5)
+
+How do I enable CORS and other HTTP features?
+---------------------------------------------
+
+Serve supports arbitrary `Starlette middlewares <https://www.starlette.io/middleware/>`_
+and custom middlewares in Starlette format. The example below shows how to enable
+`Cross-Origin Resource Sharing (CORS) <https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS>`_.
+You can follow the same pattern for other Starlette middlewares.
+
+.. note::
+
+  Serve does not list ``Starlette`` as one of its dependencies. To utilize this feature,
+  you will need to:
+
+  .. code-block:: bash
+
+    pip install starlette
+
+.. code-block:: python
+
+    from starlette.middleware import Middleware
+    from starlette.middleware.cors import CORSMiddleware
+
+    serve.init(
+        http_middlewares=[
+            Middleware(
+                CORSMiddleware, allow_origins=["*"], allow_methods=["*"])
+        ])