Handle `X-Forwarded-*` headers for OWIN

ForwardedHeadersMiddleware.cs

public class ForwardedHeadersMiddleware : OwinMiddleware
{
    public ForwardedHeadersMiddleware(OwinMiddleware next) : base(next)
    {
    }

    public override Task Invoke(IOwinContext context)
    {
        if (string.Equals(context.Request.Headers["X-Forwarded-Proto"], "https",
                StringComparison.OrdinalIgnoreCase))
        {
            context.Request.Scheme = "https";
        }

        var forwardedForHeader = context.Request.Headers["X-Forwarded-For"];
        if (!string.IsNullOrWhiteSpace(forwardedForHeader))
        {
            context.Request.RemoteIpAddress = forwardedForHeader;
        }

        var forwardedHost = context.Request.Headers["X-Forwarded-Host"];
        if (!string.IsNullOrWhiteSpace(forwardedHost))
        {
            context.Request.Host = new HostString(forwardedHost);
        }

        var forwardedPrefix = context.Request.Headers["X-Forwarded-Prefix"];
        if (!string.IsNullOrWhiteSpace(forwardedPrefix))
        {
            context.Request.PathBase = new PathString(forwardedPrefix);
        }

        return Next.Invoke(context);
    }
}