Hi Jflo,
you have an error in your template. It is not possible to disable new user account creation, which may be crucial functionality if you want to make your SyncServer available from the internet.
The problem is in docker variable SYNCSERVER_ALLOW_NEW_USER, it should be SYNCSERVER_ALLOW_NEW_USERS
see: https://github.com/mozilla-services/syncserver/blob/master/syncserver/__init__.py#L188
Please fix it, it may save some debugging why the account creation is not disabled, for people who are using your template
I can create pull request in your repository if you want.
Thanks!