func WhitelistWritableFields(fields ...string) *Enforcer {
	return E("ash/WhitelistWritableFields", fire.Only(fire.Create, fire.Update), func(ctx *fire.Context) error {
		// set new list
		ctx.WritableFields = fire.Intersect(ctx.WritableFields, fields)

		return nil
	})
}
func WhitelistWritableFields(fields ...string) *Enforcer {
	return E("ash/WhitelistWritableFields", fire.Only(fire.Create, fire.Update), func(ctx *fire.Context) error {
		// set new list
		ctx.WritableFields = fire.Intersect(ctx.WritableFields, fields)

		return nil
	})
}
// WhitelistWritableFields will enforce the authorization by making sure only the
// specified fields can be changed by the client.
//
// Note: This enforcer can only be used to authorize Create and Update operations.