make sure ssl/subdomain are covered both for both mixin and serverextension

.github/workflows/test.yml

@@ -86,14 +86,20 @@ jobs:
             db: postgres
           - python: "3.11"
             subdomain: subdomain
+            serverextension: serverextension
           - python: "3.11"
             ssl: ssl
+            serverextension: serverextension
+          - python: "3.11"
+            subdomain: subdomain
+            noextension: noextension
+          - python: "3.11"
+            ssl: ssl
+            noextension: noextension
           - python: "3.11"
             selenium: selenium
           - python: "3.11"
             main_dependencies: main_dependencies
-          - python: "3.10"
-            serverextension: serverextension
 
     steps:
       # NOTE: In GitHub workflows, environment variables are set by writing
@@ -119,6 +125,8 @@ jobs:
           fi
           if [ "${{ matrix.serverextension }}" != "" ]; then
               echo "JUPYTERHUB_SINGLEUSER_EXTENSION=1" >> $GITHUB_ENV
+          elif [ "${{ matrix.noextension }}" != "" ]; then
+              echo "JUPYTERHUB_SINGLEUSER_EXTENSION=0" >> $GITHUB_ENV
           fi
       - uses: actions/checkout@v3
       # NOTE: actions/setup-node@v3 make use of a cache within the GitHub base

jupyterhub/singleuser/extension.py

@@ -502,7 +502,7 @@ class JupyterHubSingleUser(ExtensionApp):
         # to make sure it has the desired effect
         cfg.default_url = self.default_url = self.get_default_url()
 
-        # load SSL configuration
+        # load internal SSL configuration
         cfg.keyfile = os.environ.get('JUPYTERHUB_SSL_KEYFILE') or ''
         cfg.certfile = os.environ.get('JUPYTERHUB_SSL_CERTFILE') or ''
         cfg.client_ca = os.environ.get('JUPYTERHUB_SSL_CLIENT_CA') or ''