Why you need this feature:
Regardless whether installing packages or interacting with version control / git in RStudio, there may be situations where certain URLs
are only available through a proxy.
In ODH notebooks / workbenches, if present at level of global cluster config, for the main notebook container[0], envs HTTP_PROXY and
HTTS_PROXY are filled in with the value of the corporate proxy server.

However, for i.e. accessing a Gitlab instance that is only available through a proxy, RStudio does not recognize those container-level env variables.

I found this background article: https://support.posit.co/hc/en-us/articles/200488488-Configuring-R-to-Use-an-HTTP-or-HTTPS-Proxy
and this current interesting bit in run-rstudio.sh:

https://github.com/opendatahub-io/notebooks/blob/main/rstudio/c9s-python-3.9/run-rstudio.sh#L26

Describe the solution you'd like:
@guimou Also add the env variable and value of HTTP_PROXY and HTTPS_PROXY from container envs, lowercased for purposes of RStudio, i.e.
http_proxy and https_proxy, to the global Renviron.site in run_rstudio.sh

env | grep HTTP_PROXY | tr '[:upper:]' '[:lower:]' >> /usr/lib64/R/etc/Renviron.site
env | grep HTTPS_PROXY | tr '[:upper:]' '[:lower:]' >> /usr/lib64/R/etc/Renviron.site

Anything else you would like to add:
I had a new project, with version control, where the gitlab url required passing through a proxy. Setting the two values
http_proxy=http://myproxy.com:5234
https_proxy=http://myproxy.com5234
at file ~/.Renviron allowed me to work with connections over a proxy.
The idea of this enhancement request is to add http_proxy= and https_proxy= entries to /usr/lib64/R/etc/Renviron.site

Current content is only KUBERNETES* ENV VAR like

cat /usr/lib64/R/etc/Renviron.site
KUBERNETES_SERVICE_PORT_HTTPS=443
KUBERNETES_SERVICE_PORT=443
KUBERNETES_PORT_443_TCP=tcp://172.30.0.1:443
KUBERNETES_PORT_443_TCP_PROTO=tcp
KUBERNETES_PORT_443_TCP_ADDR=172.30.0.1
KUBERNETES_SERVICE_HOST=172.30.0.1
KUBERNETES_PORT=tcp://172.30.0.1:443
KUBERNETES_PORT_443_TCP_PORT=443