multilingual_menu_urls.install

<?php

/**
 * Implements hook_install().
 */
function multilingual_menu_urls_install() {
  // Add Field Storage for Translated Link fields.
  $entity_manager = \Drupal::entityManager();
  $definition = $entity_manager->getFieldStorageDefinitions('menu_link_content')['translated_link_on'];
  $entity_manager->onFieldStorageDefinitionCreate($definition);
  $definition = $entity_manager->getFieldStorageDefinitions('menu_link_content')['translated_link_url'];
  $entity_manager->onFieldStorageDefinitionCreate($definition);
}

/**
 * Implements hook_uninstall().
 */
function multilingual_menu_urls_uninstall() {
  $entity_manager = \Drupal::entityManager();
  $definition = $entity_manager->getFieldStorageDefinitions('menu_link_content')['translated_link_on'];
  if (!empty($definition)) {
    $entity_manager->onFieldStorageDefinitionDelete($definition);
  }
  $definition = $entity_manager->getFieldStorageDefinitions('menu_link_content')['translated_link_url'];
  if (!empty($definition)) {
    $entity_manager->onFieldStorageDefinitionDelete($definition);
  }
}