/**
* Refresh an existing access token
*
* @return AccessToken
* @throws \Exception
*/
public function refreshToken()
{
$url = $this->salesforceLoginUrl . 'services/oauth2/token';
$post_data = ['grant_type' => 'refresh_token', 'client_id' => $this->clientId, 'client_secret' => $this->clientSecret, 'refresh_token' => $this->accessToken->getRefreshToken()];
$response = $this->makeRequest('post', $url, ['form_params' => $post_data]);
$update = json_decode($response->getBody(), true);
$this->accessToken->updateFromSalesforceRefresh($update);
return $this->accessToken;
}
