code: @Override
      public String getActor() {
          Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
          if (authentication != null && authentication.getPrincipal() instanceof UserDetails) {
              return ((UserDetails) authentication.getPrincipal()).getUsername();
          } else if (authentication != null && authentication.getPrincipal() instanceof String) {
              return (String) authentication.getPrincipal();
          }
          return undefienedActorName;
      }
docs: {@inheritDoc}
  
  @see org.audit4j.core.MetaData#getActor()