Add limited role for a User

This endpoint allows the client to limit a user.

The user associated with the API key must have any 'admin' or 'moderator' role.

This specified user will be assigned the 'limited' role. Limiting a user will limit notifications generated from new posts and comments. It doesn't delete any of the user's content or prevent them from generating new content while limited. Users are not notified of their limits in the UI, so if you want them to know about this, you must notify them.