Fixed #33735 -- Added async support to StreamingHttpResponse.

Thanks to Florian Vazelle for initial exploratory work, and to Nick
Pope and Mariusz Felisiak for review.

tests/middleware/tests.py

@@ -899,6 +899,28 @@ class GZipMiddlewareTest(SimpleTestCase):
         self.assertEqual(r.get("Content-Encoding"), "gzip")
         self.assertFalse(r.has_header("Content-Length"))
 
+    async def test_compress_async_streaming_response(self):
+        """
+        Compression is performed on responses with async streaming content.
+        """
+
+        async def get_stream_response(request):
+            async def iterator():
+                for chunk in self.sequence:
+                    yield chunk
+
+            resp = StreamingHttpResponse(iterator())
+            resp["Content-Type"] = "text/html; charset=UTF-8"
+            return resp
+
+        r = await GZipMiddleware(get_stream_response)(self.req)
+        self.assertEqual(
+            self.decompress(b"".join([chunk async for chunk in r])),
+            b"".join(self.sequence),
+        )
+        self.assertEqual(r.get("Content-Encoding"), "gzip")
+        self.assertFalse(r.has_header("Content-Length"))
+
     def test_compress_streaming_response_unicode(self):
         """
         Compression is performed on responses with streaming Unicode content.