Django channels stubs (#13939)

stubs/channels/@tests/django_settings.py

@@ -0,0 +1,12 @@
+SECRET_KEY = "1"
+
+INSTALLED_APPS = (
+    "django.contrib.contenttypes",
+    "django.contrib.sites",
+    "django.contrib.sessions",
+    "django.contrib.messages",
+    "django.contrib.admin.apps.SimpleAdminConfig",
+    "django.contrib.staticfiles",
+    "django.contrib.auth",
+    "channels",
+)

stubs/channels/@tests/stubtest_allowlist.txt

@@ -0,0 +1,15 @@
+# channels.auth.UserLazyObject metaclass is mismatch
+channels.auth.UserLazyObject
+
+# these one need to be exclude due to mypy error: * is not present at runtime
+channels.auth.UserLazyObject.DoesNotExist
+channels.auth.UserLazyObject.MultipleObjectsReturned
+channels.auth.UserLazyObject@AnnotatedWith
+
+# database_sync_to_async is implemented as a class instance but stubbed as a function
+# for better type inference when used as decorator/function
+channels.db.database_sync_to_async
+
+# Set to None on class, but initialized to non-None value in __init__
+channels.generic.websocket.WebsocketConsumer.groups
+channels.generic.websocket.AsyncWebsocketConsumer.groups