Upon deploying a new container, the main entrypoint script would run a

rb-site upgrade. Unfortunately, an upgrade doesn't take care of any

extension media that may be missing (something we may want to address in

the future). To ensure that the files won't be missing, it now also

performs a rb-site manage ... install-extension-media, which will go

through each extension and place the media files in the site directory.

Deployed a Docker container with an existing site directory and missing

extension media files. Saw that the new media files were installed and

accessible via the browser.