Clean up callback interfaces.

service/datastore/types.go

Index: service/datastore/types.go
diff --git a/service/datastore/types.go b/service/datastore/types.go
index 4a747e41b2783bd118d485be3d2662b25cbad807..94780f8408ba1cdb889836df6ca330d24d754559 100644
--- a/service/datastore/types.go
+++ b/service/datastore/types.go
@@ -2,11 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-package datastore
+//go:generate stringer -type=Toggle
 
-import (
-	"fmt"
-)
+package datastore
 
 // GeoPoint represents a location as latitude/longitude in degrees.
 //
@@ -49,16 +47,3 @@ const (
 	On
 	Off
 )
-
-func (b Toggle) String() string {
-	switch b {
-	case Auto:
-		return "Auto"
-	case On:
-		return "On"
-	case Off:
-		return "Off"
-	default:
-		return fmt.Sprintf("UNKNOWN_Toggle(%d)", b)
-	}
-}