[keycloak-user] Get user by username on version 1.7.0

I have a simple requirement. I need to check if a user is already present on IDM before allowing the user to register himself. I basically use the admin rest apis offered by keycloak for all my user activities. I was able to do this before 1.6.0, since there was an api to get user by username. I believe that this has been deprecated (removed completely) and replaced by get user by userId. If there any way to fulfill my need in idm 1.7.0? Regards, Kalinga