createUser({ username, firstname, lastname, passHash, salt, facebookId, facebookToken, googleId, googleToken, avatarName }) {
            let user = new User({
                username,
                firstname,
                lastname,
                passHash,
                salt,
                facebookId,
                facebookToken,
                googleId,
                googleToken,
                avatarName
            });

            return new Promise((resolve, reject) => {
                User.create(user, (err, createdUser) => {
                    if (err) {
                        return reject(err);
                    }

                    return resolve(createdUser);
                });
            });
        },