awc: read URL after a redirection

[robjtede]

Discussed in #3387

^{Originally posted by rharish101 June 4, 2024}
If I request a webpage with a URL, and the website redirects to another page, how do I get the URL of the new page once awc returns from a ClientRequest::send? This is when redirections are allowed (i.e. not disabled when building the client) in the client.