Allow disabling new user signups

[jpsim]

In some settings, it would be valuable to disable new user signups, such as systems with invite-only accounts, or with a finite set of potential users (e.g. a small office app).

[jeffreybergier]

It seems you would want to disable new user sign ups OR disable arbitrary apps from being able to create new users. I see a scenario where you have very simple iCloud/FaceBook/Google/Password sign ups/logins in your own, genuine, app on the App Store. However, anyone with the realm SDK for iOS/Android/Mac that got the hostname of your realm server (which is trivial once you have the genuine app) could sign up for an account and create their own realm at /~/mycoolrealm and store arbitrary amounts of data there. I know it seems far fetched. So maybe its a way of proving that the app that is connecting to the realm server is a genuine client. I'm not sure. But thats what I was thinking.

[monajafi]

This feature is highly required in my app too.In client side not being able to disable new user registration for non admin users is a big concern.