Support requests with https URLs

$ cat rq.txt 
GET https://ftp.debian.org/debian/README.html HTTP/1.1

$ cat rq.txt | unix2dos | socket localhost 3142
HTTP/1.1 403 Forbidden file type or location
Content-Length: 512
Content-Type: text/html
Date: Fri, 10 Sep 2021 09:05:38 GMT
Server: Debian Apt-Cacher NG/3.7.2

This is not fixed setting "AllowedUserPorts" to "80 443", some security check is in play and needs a review.