The current services API only exposes a restart action:
POST /api/servers/{server}/services/{service}/restart
For nginx in particular, a full restart drops in-flight connections, which makes it unsafe to use in automated workflows (SSL renewals, deploys, etc.).
Request: Add a reload action that maps to a graceful reload where the underlying service supports one (nginx -s reload, php-fpm reload, supervisorctl reread/update, etc.):
POST /api/servers/{server}/services/{service}/reload
For services without a meaningful reload, the endpoint could either 404 or fall back to restart with a flag in the response.
Confirmed in Discord on April 30 that no such endpoint currently exists.