in src/main/java/org/apache/sling/jcr/jackrabbit/base/security/PrincipalProviderTracker.java [135:141]
private static String getProviderName(PrincipalProvider provider,ServiceReference ref){
String providerName = (String) ref.getProperty(COMPAT_PRINCIPAL_PROVIDER_NAME);
if(providerName == null){
providerName = provider.getClass().getName();
}
return providerName;
}