Allow rewriting Response's Location header about proxykit

[datvm]

Please check the pull request. Usage:

            services.AddProxy(configureOptions: options =>
            {
                options.RewriteResponseLocationHeader = true;
            });

I still haven't understood your Unit Test yet so I will need your help on this. I have tested it with https://httpstat.us/301.

[damianh]

It appears the upstream host is not aware of or using the x-forwarded headers. If it uses those headers, it would generate the correct absolute URL in the location header. Is this not the case?

[damianh]

@datvm I've added a test #79 that ensures the location header is correct. If your upstream host is not generating the correct URLs then it is not configured to use X-Forwarded-* headers correctly. Please see the relevant section in the documentation.

Finally, if you really want or need to to do location header rewrites do it in your proxy code. Something like...

    app.RunProxy(async context =>
    {
        var response = await context
            .ForwardTo("http://localhost:" + port + "/")
            .AddXForwardedHeaders()
            .Send();
        if (response.Headers.Location != null)
        {
            response.Headers.Location = <rewrite here>;
        }
        return response;
    }));

... which could be wrapped in an extension method.

As such, I won't be accepting your proposed change.