Ignore email for unique key

[drumichael611]

Hi All --
I have configured Shield to not use an email address, but a mobile phone number instead. The user enters their mobile phone, their password and then a 2fa code is sent to their mobile phone.

Users do provide their email address, but for authentication purposes, I don't really care about it. There could even be 2 accounts (2 different mobile phone numbers) that share the same email, and that's OK for our use.

Where I'm running into a problem is when registering, if the second user has an email that's already connected to another user, I get an error like this:

Duplicate entry 'email_password-****@gmail.com' for key 'auth_identities.type_secret'.

I guess what would solve this is to set the auth_identities as 'mobilephone_password-5555555555' instead. This would make the mobile phone unique instead. I just don't quite understand how to accomplish this.

Any guidance would be appreciated!!!