Using HTTP proxy for HTTPS address does not start a HTTP Connection

[HoffmannP]

Describe the bug

When I want to access an HTTPS ressource via a HTTP Proxy the connection fails due to axios not starting a HTTP Connection via which both sides can talk but instead tries the "usual" connection to the proxy with path as the target.

To Reproduce

https://codesandbox.io/p/devbox/admiring-panini-rp2pyr

Code snippet

import axios from "axios"

const instance = axios.create({
  proxy: {
    protocol: 'http',
    host: '23.152.40.14',
    port: 3128
  }
})

instance.post(
  'https://nmshd-bkb.demo.meinbildungsraum.de/api/v1/Challenges',
  { test: 1 }
).then(
  response => { console.log('Success\n', response.data) }
).catch(
  error => {
    console.error('Error\n', error.response ? error.response.data : error.cause)
  }
)

Expected behavior

It works

Axios Version

1.6.7

Adapter Version

http

Browser

No response

Browser Version

No response

Node.js Version

19.9.0

OS

Linux Mint 21.3

Additional Library Versions

No response

Additional context/Screenshots

No response

[HoffmannP]

But it is possible to use that server to get that response if the correct way is applied: https://codesandbox.io/p/devbox/lively-meadow-j3834n

import axios from "axios";
import HttpsProxyAgent from "https-proxy-agent";

const instance = axios.create({
  httpsAgent: new HttpsProxyAgent.HttpsProxyAgent("http://23.152.40.14:3128"),
});

instance
  .post("https://nmshd-bkb.demo.meinbildungsraum.de/api/v1/Challenges", {
    test: 1,
  })
  .then((response) => {
    console.log("Success\n", response.data);
  })
  .catch((error) => {
    console.error(
      "Error\n",
      error.response ? error.response.data : error.cause,
    );
  });