RegistrationUserCreation customization doesn't work after upgrading to keycloak 21 version

1

I use keycloak as an identity provider but the users are stored in custom storage.
I created a class that extends from RegistrationUserCreation and override the validate() method to customize the validation of the registration form(my form contains “full name” instead of “first name” and “last name”.)
After updating keycloak version from 20 to 21 the class is not recognized and the original(from class RegistrationUserCreation) validate() method is called.

public class CustomRegistrationUserCreation extends RegistrationUserCreation {
     @Override
    public void validate(ValidationContext context) {
          //some code
    }
}

created file this file org.keycloak.authentication.FormActionFactory in META-INF.service which contains this line com.blabla.keycloak.formaction.CustomRegistrationUserCreation

I couldn’t find in the changelog what is changed.
What changes I should do to make it work again?