How to modify Apache config on polyanthum?

As part of #30472 (moved), we are setting up a service on polyanthum that allows bridge operators to test the TCP reachability of their obfs4 port. We would like to expose the service over a URL such as bridges.torproject.org/scan/. This seems to require a new ProxyPass directive in the file /etc/apache2/sites-enabled/bridges.torproject.org.conf.

What's the process for modifying this file? Is it under version control? If so, how do we commit a change to this version control system?

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