How to authenticate user using mobile number in Keycloak

User has a custom attribute phoneNumber in Keycloak.

There is a default method for fetching token using username and password but would it be possible to authenticate using phoneNumber / password instead of username / password.

curl
-d “client_id=$CLIENT_ID” -d “client_secret=$CLIENT_SECRET”
-d “username=$UNAME” -d “password=$PASSWORD”
-d “grant_type=password”
“$KEYCLOAKHOST/auth/realms/$REALM/protocol/openid-connect/token”

What call should I use to authenticate using a custom attribute in UserModel

So assuming UserModel contains username, phoneNumber …
What call should I use to authenticate using a custom attribute (say phoneNumber) in UserModel.

Appreciate your inputs on this