title: A new entity was found through the relationship - error
body: <p>I try to establish a simple association of two tables. But I always geht the following error:</p>
  
  <p>A new entity was found through the relationship 'Shopware\CustomModels\JoeKaffeeAbo\Client#abos' that was not configured to cascade persist operations for entity: Shopware\CustomModels\JoeKaffeeAbo\Abo@00000000211b173900000000cf7658ac</p>
  
  <p>Here are my Models:</p>
  
  <pre><code>&lt;?php
  namespace Shopware\CustomModels\JoeKaffeeAbo;
  
  use Symfony\Component\Validator\Constraints as Assert,
  Doctrine\Common\Collections\ArrayCollection,
  Shopware\Components\Model\ModelEntity,
  Doctrine\ORM\Mapping AS ORM;
  
  
  /**
   * @ORM\Entity
   * @ORM\Table(name="joe_kaffee_abo_abos")
   */
  class Abo extends ModelEntity
  {
  
      public function __construct() {
          $client = new ArrayCollection();
      }
  
      /**
       * Unique identifier
       *
       * @var integer
       * @ORM\Column(name="id", type="integer", nullable=false)
       * @ORM\Id
       * @ORM\GeneratedValue(strategy="IDENTITY")
       */
      protected $id;
  
  
  
      /**
       * @ORM\ManyToMany(targetEntity="Shopware\CustomModels\JoeKaffeeAbo\Client",     inversedBy="abos", cascade={"persist", "remove"})
       **/
      protected $clients;
  
      /**
       * @var string
       * @ORM\Column(name="name", type="string", length=255, nullable=true)
       */
      protected $name = '';
  
      /**
       * @var string
       * @ORM\Column(name="desc", type="string", length=255, nullable=true)
       */
      protected $desc = '';
  
  
      /**
       * @var string
       * @ORM\Column(name="name_en", type="string", length=255, nullable=true)
       */
      protected $name_en = '';
  
      /**
       * @var string
       * @ORM\Column(name="desc_en", type="string", length=255, nullable=true)
       */
      protected $desc_en = '';
  
  
      //getter and setters...
  }
  ?&gt;
  </code></pre>
  
  <p>Client Model:</p>
  
  <pre><code>&lt;?php
  namespace Shopware\CustomModels\JoeKaffeeAbo;
  
  use Symfony\Component\Validator\Constraints as Assert,
  Doctrine\Common\Collections\ArrayCollection,
  Shopware\Components\Model\ModelEntity,
  Doctrine\ORM\Mapping AS ORM;
  
  /**
   * @ORM\Entity
   * @ORM\Table(name="joe_kaffee_abo_client")
   */
  class Client extends ModelEntity
  {
      public function __construct() {
          $this-&gt;abos = new ArrayCollection();
      }
  
      /**
       * Unique identifier
       *
       * @var integer
       * @ORM\Column(name="id", type="integer", nullable=false)
       * @ORM\Id
       * @ORM\GeneratedValue(strategy="IDENTITY")
       */
      protected $id;
  
      /**
       * @ORM\ManyToMany(targetEntity="Shopware\CustomModels\JoeKaffeeAbo\Abo", mappedBy="clients", cascade={"persist", "remove"})
       **/
      protected $abos = null;
  
      public function addAbo($abo)
      {
          $abo-&gt;addClient($this);
          $this-&gt;abos[] = $abo;
      }
  
  
      /**
       * @var integer
       * @ORM\Column(name="customerid", type="integer", nullable=true)
       */
      protected $customerid;
  
      /**
       * @var integer
       * @ORM\Column(name="customernumber", type="integer", nullable=true)
       */
      protected $customernumber;
  
      /**
       * @var boolean
       * @ORM\Column(name="is_active", type="boolean", nullable=true)
       */
      protected $is_active;
  
      //Getters and Setters
  }
  ?&gt;
  </code></pre>
  
  <p>The error occurs after I executed the following statements:</p>
  
  <pre><code>$client = new Client();
  $client-&gt;setCustomerid(12);
  $client-&gt;setCustomernumber(12);
  $client-&gt;setIs_active(true);
  Shopware()-&gt;Models()-&gt;persist($client);
  
  $abo = new Abo();       
  $abo-&gt;setName("name");
  $abo-&gt;setDesc("desc");
  $abo-&gt;setName_en("name");
  $abo-&gt;setDesc_en("desc");
  
  $client-&gt;addAbo($abo);
  //$abo-&gt;addClient($client);
  //$client-&gt;addAbo($abo);
  
  Shopware()-&gt;Models()-&gt;persist($client);
  //Shopware()-&gt;Models()-&gt;persist($abo);
  Shopware()-&gt;Models()-&gt;flush();
  </code></pre>