Polishing.

Use mapNotNull(…) instead of filter + map.

See #3413

src/main/antora/modules/ROOT/pages/auditing.adoc

@@ -109,10 +109,9 @@ class SpringSecurityAuditorAware implements ReactiveAuditorAware<User> {
   public Mono<User> getCurrentAuditor() {
 
     return ReactiveSecurityContextHolder.getContext()
-                .filter(it -> it.getAuthentication() != null)
-                .map(SecurityContext::getAuthentication)
+                .mapNotNull(SecurityContext::getAuthentication)
                 .filter(Authentication::isAuthenticated)
-                .map(Authentication::getPrincipal)
+                .mapNotNull(Authentication::getPrincipal)
                 .map(User.class::cast);
   }
 }