D8_rplf/core/modules/rest/rest.module

<?php

/**
 * @file
 * RESTful web services module.
 */

use Drupal\Core\Routing\RouteMatchInterface;

/**
 * Implements hook_help().
 */
function rest_help($route_name, RouteMatchInterface $route_match) {
  switch ($route_name) {
    case 'help.page.rest':
      $output = '';
      $output .= '<h3>' . t('About') . '</h3>';
      $output .= '<p>' . t('The RESTful Web Services module provides a framework for exposing REST resources on your site. It provides support for content entities (see the <a href=":field">Field module help page</a> for more information about entities) such as content, users, taxonomy terms, etc.; REST support for content items of the Node module is enabled by default, and support for other types of content entities can be enabled. Other modules may add support for other types of REST resources. For more information, see the <a href=":rest">online documentation for the RESTful Web Services module</a>.', [':rest' => 'https://www.drupal.org/documentation/modules/rest', ':field' => (\Drupal::moduleHandler()->moduleExists('field')) ? \Drupal::url('help.page', ['name' => 'field']) : '#']) . '</p>';
      $output .= '<h3>' . t('Uses') . '</h3>';
      $output .= '<dl>';
      $output .= '<dt>' . t('Installing supporting modules') . '</dt>';
      $output .= '<dd>' . t('In order to use REST on a web site, you need to install modules that provide serialization and authentication services. You can use the Core module <a href=":hal">HAL</a> for serialization and <a href=":basic_auth">HTTP Basic Authentication</a> for authentication, or install a contributed or custom module.', [':hal' => (\Drupal::moduleHandler()->moduleExists('hal')) ? \Drupal::url('help.page', ['name' => 'hal']) : '#', ':basic_auth' => (\Drupal::moduleHandler()->moduleExists('basic_auth')) ? \Drupal::url('help.page', ['name' => 'basic_auth']) : '#']) . '</dd>';
      $output .= '<dt>' . t('Enabling REST support for an entity type') . '</dt>';
      $output .= '<dd>' . t('REST support for content items of the Node module is enabled by default, and support for other types of content entities can be enabled. To enable support, you can use a <a href=":config">process based on configuration editing</a> or the contributed <a href=":restui">Rest UI module</a>.', [':config' => 'https://www.drupal.org/documentation/modules/rest', ':restui' => 'https://www.drupal.org/project/restui']) . '</dd>';
      $output .= '<dd>' . t('You will also need to grant anonymous users permission to perform each of the REST operations you want to be available, and set up authentication properly to authorize web requests.') . '</dd>';
      $output .= '</dl>';
      return $output;
  }
}