src/Core/OAuth/OAuth2/OAuth2LoginHelper.php
private function constructRefreshTokenHeader(){
        $authorizationHeaderInfo = $this->generateAuthorizationHeader();
        $http_header = array(
            'Accept' => CoreConstants::CONTENTTYPE_APPLICATIONJSON,
            'Authorization' => $authorizationHeaderInfo,
            'Content-Type' => CoreConstants::CONTENTTYPE_URLFORMENCODED,
            'connection'    => 'close'
        );
        return $http_header;
    }
private function constructRefreshTokenHeader(){
        $authorizationHeaderInfo = $this->generateAuthorizationHeader();
        $http_header = array(
            'Accept' => CoreConstants::CONTENTTYPE_APPLICATIONJSON,
            'Authorization' => $authorizationHeaderInfo,
            'Content-Type' => CoreConstants::CONTENTTYPE_URLFORMENCODED,
            'connection'    => 'close'
        );
        return $http_header;
    }
Generate header for refresh Token
@return Array Refresh Token header