Describe the bug

The URL to launch the notebook got corrupted when we upgraded the Jupyter Notebook version to 7.0.0rc0 and the Jupyter Lab version to 4.0.2 (JN version 7.0.0rc0 warranted an upgrade from 4.0.0 to 4.0.2 in Lab). When we launch the hub, it loads a URL - Hub_URL/user/xx/user/xx/user/xx/lab that repeats "user/username" thrice and as a result returns a 404 error. This has been reported by multiple users within Berkeley who tested the deployment. Previously, we had Notebook 7.0.0b3 and Lab 4.0.0 which did not have the URL corruption issue.

I am not sure whether this is a Lab specific issue or a notebook-specific issue. Please redirect me to the right repository if I am mistaken here. @ryanlovett

To Reproduce
Steps to reproduce the behavior:

1. Upgrade Notebook to 7.0.0rc0
2. Upgrade Lab to 4.0.2
3. Try launching the hub
4. See 404 error because of URL getting corrupted

Expected behavior
Notebook should launch without any URL corruption issues

Screenshots

Desktop (please complete the following information):

• OS: Windows/Mac
• Browser: Firefox/Safari

Additional context
Add any other context about the problem here.