final String message =
messages.getMessage("message.body.grouping.change.shift", registration.getNumber().toString(), studentGroup
.getGroupNumber().toString(), executionCourseNames.toString());
final String groupName = messages.getMessage("message.group.name", studentGroup.getGroupNumber());
final Collection<Recipient> recipients =
Collections.singletonList(new Recipient(groupName, UserGroup.of(Person.convertToUsers(recievers))));
SystemSender systemSender = Bennu.getInstance().getSystemSender();
new Message(systemSender, systemSender.getConcreteReplyTos(), recipients,
messages.getMessage("message.subject.grouping.change"), message, "");
}