Tests: added ASGI HTTP applications.

test/python/server_port/asgi.py

@@ -0,0 +1,11 @@
+async def application(scope, receive, send):
+    assert scope['type'] == 'http'
+
+    await send({
+        'type': 'http.response.start',
+        'status': 200,
+        'headers': [
+            (b'content-length', b'0'),
+            (b'server-port', str(scope['server'][1]).encode()),
+        ]
+    })