farmOS/modules/farm/farm_client/farm_client.module

<?php

/**
 * @file
 * Farm Client module.
 */

/**
 * Implements hook_farm_api_oauth2_client().
 */
function farm_client_farm_api_oauth2_client() {
  $clients = array();

  $clients['farm_client'] = array(
    'label' => 'farmOS Client (Field Kit)',
    'client_key' => 'farm_client',
    'redirect_uri' => '',
  );

  return $clients;
}