Unable to start devbox VM behind corporate proxy

🐛 bug report

Preflight Checklist

• I have read the Contributing Guidelines for this project.
• I agree to follow the Code of Conduct that this project
  adheres to.
• I have searched the issue tracker for an issue that matches the one I want
  to file, without success: => related, but no solution: https://github.com/codesandbox/codesandbox-client/issues/8074

Description of the problem

We are behind a corporate proxy. We cannot start any sandbox VM or devbox.

In our company all HTTP(S) traffic must go through that proxy. The proxy is configured correctly in the browser. We tested on several different browsers: Firefox, Chorme & Edge. Always the same result.

How has this issue affected you? What are you trying to accomplish?

Goal: Just start any codesandbox VM or devBox.

To Reproduce

1. https://codesandbox.io/dashboard/
2. Click on "Create" button
3. Choose "JavaScript"
4. Choose "Devbox"
5. Click "Create DevBox"

The browser starts and starts a VM, but then an error popup is shown: "The workbench failed to connect to the server (Error: WebSocket close with status code 1006)". First error message in browser console is:

websocket-factory.ts:57 WebSocket connection to 'wss://jpkfpt-50000.vscode.codesandbox.io/stable-dc96b837cf6bb4af9cd736aa3af08cf8279f7685?reconnectionToken=eb0cd615-3695-4e3a-ae87-602e9e885a60&reconnection=false&skipWebSocketFrames=false&preview_token=eyJhbGciXXXXXXXXXXXXXXX....XXXXX' failed

Link to sandbox: link

Your Environment

Start by reproducing the Devbox creation flow and inspect the first browser-console failure at websocket-factory.ts:57, especially the WebSocket connection shown in the report. Done means a Devbox can start and its workbench connects successfully when HTTP(S) traffic is routed through a corporate proxy.