Phone number sign-in

The next popular sign-in method is using a mobile phone number. A user enters their phone number to receive a one-time verification code, also known as OTP, one-time password. There are many use cases in which the application requires two layers of authentication. Even after email login, the business logic of the application expects a phone number verification. To enable phone number sign-in through Firebase UI, all we need to do is enable the phone number sign-in method in Firebase console.