Prevent username enumeration while registering a user in keycloak

Question

I'm currently working with Keycloak version 16.1.1. During user registration, if an email that is already present in the database is entered, keyclaok generates an "email_in_use" error. I aim to modify this behavior. Specifically, when a user attempts to register with an email that already exists, I want to redirect him to the successful registration page. On this page, the user will be prompted to click a link sent to his email inbox for verification.

in the registration flow, I created a copy of the registration flow where I replaced the "Profile Validation" execution with a new ProfileValidationIgnoreEmailInUse execution.

public class ProfileValidationIgnoreEmailInUse implements FormAction, FormActionFactory {
@Override
    public void validate(ValidationContext context) {
    // copied the same code as org.keycloak.authentication.forms.RegistrationProfile, but I modified the email check part
    ...
    if (emailValid && !context.getRealm().isDuplicateEmailsAllowed() && context.getSession().users().getUserByEmail(email, context.getRealm()) != null) {
            logger.infof("TTEST skipped error email in use");
        }
    ... 
    }
}

Now when the user enters an existing email in the register form, I get a new error: ConstraintViolationException: could not execute statement at org.keycloak.storage.UserStorageManager.addUser(UserStorageManager.java:247) which is normal because the username already exists in the database. What would be the next change I have to make in order to ignore this ConstraintViolationException exception?