We have introduced a user self-registration process, to allow users to enter their own passwords and phone numbers.   

In Settings > Users, enable the "Send Registration Emails" toggle.  Once enabled, every new user will be sent an email containing a link to a registration page where they can enter their details.

We request the user's phone number so that we can send password reset and Two-Factor Authentication codes.  It will not be used for any other purpose or shared.  The number may be a mobile or land-line.