Here are more explanations regarding my contraints:
For security reasons I don't want to manage the app's secrets under GIT
My app's secrets can't be managed by certificates
I don't want to build a new app each time secrets change
I want to manage theses secrets through files
To manage all these contraints, I think the best way is to deploy my custom app in two steps:
deploy custom app on device
deploy files on device into custom app Library folder
That's why I'm looking for something to install
remotely files into app data container (Library folder) once the app is already on device.