Multiple accounts with same email and maintainer field

[mcarans]

I have 3 accounts using same email address, but maintainer field relies on email address to search and does not pick the right one, so I get "Maintainer: The user with email "@.com" is not part of this organization."

Where there is more than one account with same email, either:

1. need the ability to select the correct account and display it in UI
   or
2. only allow users to register with a unique email address and make it a required field upon register