public function getRules()
    {
        $rules = [
            static::FIRST_NAME => "required|max:100",
            static::LAST_NAME => "required|max:100",
            static::EMAIL => "required|max:100|email|unique:users,email,{$this->id},id",
        ];
        if (!$this->id) {
            $rules[static::PWD_FIELD] = 'required|min:' . config('app.model.user.password.min', 6)
                . '|max:' . config('app.model.user.password.max', 20);
        }
        return $rules;
    }