Remove the depandancy of email as a required form element in registration forms

[svenl77]

Description
I just got a support ticket from a customer using the mobile numbers as an identifier. He makes me aware that email is not needed in WP/BuddyPress and that many younger people not like email anymore. And it makes sense for me. Younger people only use their phones.

The steps to reproduce the issue
Create a registration form without the user email field and try to use it. You will get an error that the email field is required.

Expected behavior
Make registration work with username and password only.

Link to the ticket: https://secure.helpscout.net/conversation/838374807/25126/?folderId=573402

Questions

1. How to sent an activation link to a mobile phone number. There must be a way to verify the user owns the number and has permission to create the account

There is a plugin for this https://codecanyon.net/item/digits-wordpress-mobile-number-signup-and-login/19801105

Maybe we can write an extension for this plöugin or rebuild the logic so we are not depending on this plugin.

[svenl77]

Just got some related feedback

It will also be the same of course for sites that want to use facebook login etc instead of email address
--> I believe that Facebook provide the email address but want to add the feedback here so we can take care.