Add icons to mailbox owner select

dashboard/src/components/MailboxDialog.vue

@@ -101,6 +101,7 @@ defineExpose({
 
     // unify on .name for multiselect
     usersAndGroups.value.forEach(u => {
+      u.icon = u.name ? 'fa-solid fa-users' : (u.username ? 'fa-solid fa-user' : 'fa-solid fa-cube') ;
       u.name = u.name || u.username || u.label || u.fqdn;
     });