Add session_application helper to django routing

Author: SmileyChris

graphql_ws/django/routing.py

@@ -1,4 +1,5 @@
 from channels.routing import ProtocolTypeRouter, URLRouter
+from channels.sessions import SessionMiddlewareStack
 from django.apps import apps
 from django.urls import path
 from .consumers import GraphQLSubscriptionConsumer
@@ -13,6 +14,10 @@
 
 application = ProtocolTypeRouter({"websocket": URLRouter(websocket_urlpatterns)})
 
+session_application = ProtocolTypeRouter(
+    {"websocket": SessionMiddlewareStack(URLRouter(websocket_urlpatterns))}
+)
+
 if AuthMiddlewareStack:
     auth_application = ProtocolTypeRouter(
         {"websocket": AuthMiddlewareStack(URLRouter(websocket_urlpatterns))}