[bug] getting "HTTP/1.1 501 Not Implemented"

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### Describe the bug

hi,
i like the idea of your proxy, but, getting `HTTP/1.1 501 Not Implemented` for `curl -v --proxy http://localhost:8080 -k https://worldtimeapi.org/api/timezone/Asia/Jerusalem`.
what am i missing? how can i make it work?

### Logs

```shell
user1@user1-pc:~/Downloads$ curl -v --proxy http://localhost:8080 -k https://worldtimeapi.org/api/timezone/Asia/Jerusalem
* Trying 127.0.0.1:8080...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 8080 (#0)
* allocate connect buffer!
* Establish HTTP proxy tunnel to worldtimeapi.org:443
> CONNECT worldtimeapi.org:443 HTTP/1.1
> Host: worldtimeapi.org:443
> User-Agent: curl/7.68.0
> Proxy-Connection: Keep-Alive
>
< HTTP/1.1 501 Not Implemented
<
* Received HTTP code 501 from proxy after CONNECT
* CONNECT phase completed!
* Closing connection 0
curl: (56) Received HTTP code 501 from proxy after CONNECT
```

### Additional information

see Reproduction url for code

### Reproduction

https://jsfiddle.net/g2fk1vph/

The issue names no repository files, tests, or entry points. Start by reproducing the curl CONNECT request against the proxy and trace how CONNECT requests are handled; done means the HTTPS request succeeds through the proxy and a regression test covers this case.

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