opensupports/server/models/ERRORS.php

<?php
class ERRORS {
    const INVALID_CREDENTIALS = 'User or password is not defined';
    const SESSION_EXISTS = 'User is already logged in';
    const NO_PERMISSION = 'You have no permission to access';
    const INVALID_TITLE = 'Invalid title';
    const INVALID_CONTENT = 'Invalid content';
}