system/HTTP/CURLRequest.php
protected function prepareURL(string $url): string
	{
		// If it's a full URI, then we have nothing to do here...
		if (strpos($url, '://') !== false)
		{
			return $url;
		}

		$uri = $this->baseURI->resolveRelativeURI($url);

		return (string) $uri;
	}
protected function prepareURL(string $url): string
	{
		// If it's a full URI, then we have nothing to do here...
		if (strpos($url, '://') !== false)
		{
			return $url;
		}

		$uri = $this->baseURI->resolveRelativeURI($url);

		return (string) $uri;
	}
If the $url is a relative URL, will attempt to create
a full URL by prepending $this->baseURI to it.

@param string $url

@return string