Users can authenticate using just their email or phone number. On their first time using Cotter, they will be prompted with a verification code.
On their first ever signup to a website/app that uses Cotter, the user have to enter a verification code.
The user will then enter the verification code.
After the first signup, anytime the user need to sign-up or login to any website or app that uses Cotter, the user just needs to enter the email or phone number they want to use, and they'll be instantly verified.