Set Content-Security-Policy response header on VSCode Server web UI

Question

I am using the vscode server behind a reverse proxy inside the jupyerlab extension proxy and I would like to modify the Content-Security-Policy response header. Specifically I would like to modify the frame ancestor to the domain URL which is used to connect. Otherwise I get a "Refused to load https://xxxx because it does not appear in the frame-ancestors directive of the Content Security Policy". If I enforce it on the reverse proxy it works, but I would rather want it enforced from the sender of the response. Anyone knows how to solve this?