chore(server): Required authentication by default. Reloves argoproj#5206

Signed-off-by: Alex Collins <alex_collins@intuit.com>

cmd/argo/commands/server.go

@@ -148,7 +148,7 @@ See %s`, help.ArgoSever),
 	// "-e" for encrypt, like zip
 	command.Flags().BoolVarP(&secure, "secure", "e", false, "Whether or not we should listen on TLS.")
 	command.Flags().BoolVar(&htst, "hsts", true, "Whether or not we should add a HTTP Secure Transport Security header. This only has effect if secure is enabled.")
-	command.Flags().StringArrayVar(&authModes, "auth-mode", []string{"server"}, "API server authentication mode. Any 1 or more length permutation of: client,server,sso")
+	command.Flags().StringArrayVar(&authModes, "auth-mode", []string{"client"}, "API server authentication mode. Any 1 or more length permutation of: client,server,sso")
 	command.Flags().StringVar(&configMap, "configmap", "workflow-controller-configmap", "Name of K8s configmap to retrieve workflow controller configuration")
 	command.Flags().BoolVar(&namespaced, "namespaced", false, "run as namespaced mode")
 	command.Flags().StringVar(&managedNamespace, "managed-namespace", "", "namespace that watches, default to the installation namespace")