url:SetURL(url$[, flags])
When successfully setting a new URL, relative or absolute, the handle contents will be replaced with the information of the newly get URL.
Pass a string to the url$ parameter. The string must point to a correctly
formatted RFC 3986+ URL.
You can also pass Nil to unset the URL in the URL handle.
The optional flags parameter can be a combination of flags as described in
the documentation of the hurl.URL() function. See hurl.URL for details.
Unless #CURLU_NO_AUTHORITY is get, a blank host name is not allowed in the URL.