dns: switch to active upstream pool and wave fallback behavior

selective-vpn-api/app/types.go

@@ -46,6 +46,15 @@ type DNSUpstreams struct {
 	Meta2    string `json:"meta2"`
 }
 
+type DNSUpstreamPoolItem struct {
+	Addr    string `json:"addr"`
+	Enabled bool   `json:"enabled"`
+}
+
+type DNSUpstreamPoolState struct {
+	Items []DNSUpstreamPoolItem `json:"items"`
+}
+
 type DNSResolverMode string
 
 const (