With the implementation of the HTTP proxy it would be great to have an environment variable VSCODE_HTTP_REFERER available to build custon URLs for proxied webview requests.

This feature helps solving REditorSupport/vscode-R#275. The existence of such an environment variable also allows to differentiate a local (VS Code) installation from a server (code-server) installation.

Other server-based IDEs set an environment variable based on the HTTP referer when the client session is initialized. See https://github.com/rstudio/rstudio/blob/aa266ded96123f654e5f3163cde39697744eee89/src/cpp/session/SessionClientInit.cpp#L170 for example.

Could you implement something similar in code-server? Or is the information on the HTTP referer already available somewhere else?