feat: derpmap field in config (#1823)

hscontrol/derp/derp.go

@@ -82,6 +82,9 @@ func mergeDERPMaps(derpMaps []*tailcfg.DERPMap) *tailcfg.DERPMap {
 
 func GetDERPMap(cfg types.DERPConfig) *tailcfg.DERPMap {
 	var derpMaps []*tailcfg.DERPMap
+	if cfg.DERPMap != nil {
+		derpMaps = append(derpMaps, cfg.DERPMap)
+	}
 
 	for _, path := range cfg.Paths {
 		log.Debug().

hscontrol/types/config.go

@@ -176,6 +176,7 @@ type DERPConfig struct {
 	STUNAddr                           string
 	URLs                               []url.URL
 	Paths                              []string
+	DERPMap                            *tailcfg.DERPMap
 	AutoUpdate                         bool
 	UpdateFrequency                    time.Duration
 	IPv4                               string