Feature: The parameter podman_credential_files is used to provide containers-auth.json files which allow authentication to registries. See README.md for more infomation. Reason: Users need a way to provide credential files for authenticating to private registries. Some operations may need to pull images from registries in an automated or unattended way, and cannot use `registry_username` and `registry_password`. Result: Users can provide registry credentials for automated and unattended operations.