* Ensure PolicyKit autorization before editing system connections, and request secrets from the system settings service for system connections. This requires splitting each CEPage subclass's *_new() method into two parts, the first doing minimal setup, and the second filling in the UI with details from the backing NMConnection. Between the first and second parts, if required, secrets are requested from the system settings service using PolicyKit. As a bonus, actually handle errors instead of dropping them on the floor.