Use Environment Variable or Parameter Variable as part of url

### What feature do you want to see added?

In the webhook url, allow us to pass some variable (parameters) or environment variable like ${BUILD_NUMBER}.


We tried passing ${BUILD_NUMBER} in the url, and this is the output: it didn't render the build number into the actual build number.


### Upstream changes

_No response_

Start by locating where the outbound webhook URL is assembled and how Jenkins build variables are handled. Check whether BUILD_NUMBER or parameter variables are available at that entry point, then verify that a URL containing ${BUILD_NUMBER} receives the resolved value in a webhook request. Done means variable expansion works reliably in webhook URLs.

Written by the indexing model from the issue text.