protected void saveAuthorizationGrant(ServerAuthorizationCodeGrant grant) {
   String encrypted = ModelEncryptionSupport.encryptCodeGrant(grant, key);
   grant.setCode(encrypted);
   grants.add(encrypted);
 }
 @Override
 public ServerAuthorizationCodeGrant removeCodeGrant(String code) throws OAuthServiceException {
   grants.remove(code);
   return ModelEncryptionSupport.decryptCodeGrant(this, code, key);
 }