title: How to configure apcu for doctrine in Symfony5
body: <p>In Symfony4 I was using the following configuration for doctrine apcu caching:</p>
  
  <pre><code>doctrine:
      orm:
          auto_mapping: true
          auto_generate_proxy_classes: false
          metadata_cache_driver: apcu
          query_cache_driver: apcu
          result_cache_driver: apcu
  </code></pre>
  
  <p>After upgrading to Symfony5 I am getting an error:</p>
  
  <blockquote>
    <p>Unknown cache of type "apc" configured for cache "metadata_cache" in entity 
       manager "default".                                                          </p>
  </blockquote>
  
  <p>When changing the it to the following configuration it works:</p>
  
  <pre><code>doctrine:
      orm:
          auto_mapping: true
          auto_generate_proxy_classes: false
          metadata_cache_driver:
              type: pool
              pool: doctrine.system_cache_pool
          query_cache_driver:
              type: pool
              pool: doctrine.system_cache_pool
          result_cache_driver:
              type: pool
              pool: doctrine.result_cache_pool
  </code></pre>
  
  <p>But what kind of cache am I using now? And how can I switch it to apcu?</p>