person.addToRelatedPersons(anotherPerson);
anotherPerson.addToRelatedPersons(person);

anotherPerson.save();
person.save();

Person {

 static hasMany = [relatedPersons:Person];

}

Set<Folder> folders = message.getFolders();
   folders.remove(folder);
   folders.add(trashFolder);
   message.setFiles(folders);
MESSAGESDAO.getMessageDAO().save(message);

message.setFiles(folders);

Set<Folder> folders = message.getFolders();
   folders.remove(folder);
   folders.add(trashFolder);
MESSAGESDAO.getMessageDAO().save(message);