Description of problem: Cockpit does not provide a way to configure NTP clients. There should be a way to set the NTP servers a client should sync with. This should be a high level API which takes care to perform the necessary platform tasks (service restarts if needed).
We currently have settings that enable/disable NTP ... but not yet to configure which server to use. A file based configuration API is available: We would simply files in /etc/systemd/timesyncd.conf.d/ to add and remove NTP servers. See 'man timesyncd.conf'
https://github.com/cockpit-project/cockpit/wiki/Feature:-Time-Sync-Configuration
https://trello.com/c/sjoetDb0/140-time-sync-configuration
https://trello.com/c/sjoetDb0/140-0-81-time-sync-configuration