Configure HTTP->HTTPS redirect

backend/app/app.yaml

@@ -10,4 +10,6 @@ handlers:
   # required when static routes are defined, but can be omitted (along with
   # the entire handlers section) when there are no static files defined.
 - url: /.*
-  script: auto
+  script: auto
+  secure: always
+  redirect_http_response_code: 301