Want to be able to use remote files in MODS_FILE

### Enhancement Type

Improve an existing feature

### Describe the enhancement

I have an online server_mod_list.txt file instead of a local server_mod_list.txt file. I hope to be able to update the online server_mod_list.txt file and restart multiple servers to achieve the upgrade, instead of going to the server to modify the file.

Or is there any way to download the remote file to the container for me when the container starts? I tried use `command`, but it didn't seem to work.

Start by tracing how MODS_FILE is handled during container startup and how the command option is invoked. The issue leaves two possible outcomes: direct support for a remote server_mod_list.txt file or a documented way to download it when the container starts; completion should clearly choose and verify one workflow.

Written by the indexing model from the issue text.