24d9677c0f
Introduce a way to configure servers that can be used to dynamically update DS records during KSK rollovers. The update-ds configuration option is a zone only option and may reference a parental-agents statement. Add some checkconf checks similar to parental-agents, like the option being at the wrong level, a duplicate list, an empty list, at the wrong zone type, and a reference to parental-agents not found.