Ability to specify the full path to the media directory in the configuration file

Is your feature request related to a problem? Please describe

I need to be able to set an absolute path to the directory with media files.

Describe the solution you'd like

I would like to have an app.mediaDirectory option, for example app.mediaDirectory=/var/lib/castopod/media.

Describe alternatives you've considered

When I set app.mediaRoot to /var/lib/castopod/media, it results in broken links that look like this: https://domain//var/lib/castopod/media/podcast/.... I also tried to patch app/Helpers/media_helper.php, but it doesn't seem to be enough to make it work and it's not a proper long-term solution.

Additional context

I'm trying to package castopod for NixOS, which has a clear separation of code, state, and configuration. Writing to any directory in the castopod directory is not an option, so I had to patch some files to make it possible (such as the writable directory location and .env file location). The only remaining issue for me now is the media handling. It would be great if these could be changed via config file, environment variables or something else.