// both the old and the new formats.
func (d *PolicyDoc) parseJSON(data []byte) error {
	json := jsoniter.ConfigCompatibleWithStandardLibrary
	var doc PolicyDoc
	err := json.Unmarshal(data, &doc)
	if err != nil {
		err2 := json.Unmarshal(data, &doc.Policy)
		if err2 != nil {
			// Just return the first error.
			return err
		}
		d.Policy = doc.Policy
		return nil
	}
	*d = doc
	return nil
}