Add Taxonomy Term to a Node's Breadcrumb in Drupal 8

Breadcrumbs.php

<?php
// src/Breadcrumbs.php

namespace Drupal\modulename;

use Drupal\Core\Breadcrumb\BreadcrumbBuilderInterface;
use Drupal\Core\Routing\RouteMatchInterface;

use Drupal\Core\Breadcrumb\Breadcrumb;
use Drupal\Core\Link;
use Drupal\Core\StringTranslation\StringTranslationTrait;
use Drupal\node\NodeInterface;

/**
 * Class Breadcrumbs.
 *
 * @package Drupal\modulename
 */
class Breadcrumbs implements BreadcrumbBuilderInterface {

  use StringTranslationTrait;

  /**
   * {@inheritdoc}
   */
  public function applies(RouteMatchInterface $route_match) {
    return $route_match->getRouteName() == 'entity.node.canonical'
    && $route_match->getParameter('node') instanceof NodeInterface;;
  }

  /**
   * {@inheritdoc}
   */
  public function build(RouteMatchInterface $route_match) {

    $node = $route_match->getParameter('node');
    $breadcrumb = new Breadcrumb();

    // By setting a "cache context" to the "url", each requested URL gets it's own cache.
    // This way a single breadcrumb isn't cached for all pages on the site.
    $breadcrumb->addCacheContexts(["url"]);

    // By adding "cache tags" for this specific node, the cache is invalidated when the node is edited.
    $breadcrumb->addCacheTags(["node:{$node->nid->value}"]);

    // Add "Home" breadcrumb link.
    $breadcrumb->addLink(Link::createFromRoute($this->t('Home'), '<front>'));

    // Given we have a taxonomy term reference field named "field_section", and that field has data,
    // Add that term as a breadcrumb link.
    if (!empty($node->field_section->entity)) {
      $breadcrumb->addLink($node->field_section->entity->toLink());
    }
    return $breadcrumb;
  }
}

modulename.services.yml

# modulename.services.yml
services:
  modulename.breadcrumbs:
    class: Drupal\modulename\Breadcrumbs
    tags:
      - { name: breadcrumb_builder, priority: 100 }