Some routers have the ability to serve DNS zones without an upstream server (for instance, Cisco IOS routers have had this since a very long time) . This feature request is about adding this capability to VyOS.
USE CASE FOR THE REQUESTED FEATURE
Infrastructure-light sites (e.g., branch offices) might not contain servers at all (there might just be appliances like storage or VoIP stuff), yet having DNS is useful, for instance for people being able to access the appliances through a name, or to ease the task of roaming field engineers -- it's always simpler to "ping wifiap" rather than rummaging through the docs to see what the AP address is on a particular site.
Being able to provide this without adding complexity to the setup is, in my opinion, a good thing.
The PowerDNS recursor has a feature to serve static zones. The attached patch adds commands to setup zones and zone records (and a few more things I happen to use sometimes, like additional options for the recursor). All the added commands are under service dns forwarding advanced. This is not supposed to be their definite placement, it's just to avoid any conflict with official commands in my custom builds.