src/Auth/ApplicationOnlyAuth.php
protected function getBearerTokenCredentials()
    {
        $signingKey = rawurlencode($this->getConsumerKey()) . ':' . rawurlencode($this->getConsumerSecret());

        return base64_encode($signingKey);
    }
protected function getBearerTokenCredentials()
    {
        $signingKey = rawurlencode($this->getConsumerKey()) . ':' . rawurlencode($this->getConsumerSecret());

        return base64_encode($signingKey);
    }
Generate bearer token credentials

@return string  Bearer token credentials