@Override
    public String resolveUsernameInternal(final RegisteredServiceUsernameProviderContext context) {
        LOGGER.debug("Returning the default principal id [{}] for username.", context.getPrincipal().getId());
        return context.getPrincipal().getId();
    }
Resolves the username for the service to be the default principal id.

@author Misagh Moayyed
@since 4.1.0
core/cas-server-core-services-api/src/main/java/org/apereo/cas/services/DefaultRegisteredServiceUsernameProvider.java