public function authenticate()
    {
        $request = new Request($this->handler);
        $this->token = $request->execute(
            RequestMethods::HTTP_POST,
            $this->makeUrl(RequestMethods::DOMUSERP_API_PEDIDOVENDA . '/auth'),
            [
                'json' => [
                    'login'    => $this->username,
                    'password' => $this->password
                ]
            ]
        )->token;

        return $this;
    }