title: Prevent new WordPress users from logging in until manually "activated"?
body: <p>I'm developing a plugin for WordPress which has 3 groups of users.  I need to disable some users and prevent them from login.  what I mean isn't preventing them to access the backend.  I want to prevent them from is log in.  For example, when they want to login they should see a message like this account isn't active yet.
  thank you guys.</p>