Put HttpResponse into good use

[jangko]

Currently HttpResponse is not being used anywhere, it would be very useful if we can put it into use like in chronos' HttpResponseRef.

Recently I found, chronos HttpRequestRef.getResponse along with it's returned HttpResponseRef is very helpful to implement CORS.

Why it is useful?
When dealing with CORS, there might be preflight request that can be responded immediately. But for simple CORS request, such as using GET or POST method, CORS handler do not respond immediately, but only add some headers to the response. There the HttpResponse will be handy.

nim-websock/websock/http/common.nim

Line 50 in f2fb0c3

HttpResponse* = ref object of HttpCommon