hostinfo: add Home Assistant Add-On detection (#8857)

Fixes #8856

Signed-off-by: Shayne Sweeney <shayne@tailscale.com>

hostinfo/hostinfo.go

@@ -150,6 +150,7 @@ const (
 	Kubernetes         = EnvType("k8s")
 	DockerDesktop      = EnvType("dde")
 	Replit             = EnvType("repl")
+	HomeAssistantAddOn = EnvType("haao")
 )
 
 var envType atomic.Value // of EnvType
@@ -255,6 +256,9 @@ func getEnvType() EnvType {
 	if inReplit() {
 		return Replit
 	}
+	if inHomeAssistantAddOn() {
+		return HomeAssistantAddOn
+	}
 	return ""
 }
 
@@ -364,6 +368,13 @@ func inDockerDesktop() bool {
 	return false
 }
 
+func inHomeAssistantAddOn() bool {
+	if os.Getenv("SUPERVISOR_TOKEN") != "" || os.Getenv("HASSIO_TOKEN") != "" {
+		return true
+	}
+	return false
+}
+
 // goArchVar returns the GOARM or GOAMD64 etc value that the binary was built
 // with.
 func goArchVar() string {