title: How to define the descriminator column as ENUM for Class Table Inheritance in Doctrine's?
body: <p>I want to implement the <a href="https://www.doctrine-project.org/projects/doctrine-orm/en/2.6/reference/inheritance-mapping.html#class-table-inheritance" rel="nofollow noreferrer">Class Table Inheritance</a>:</p>
  
  <pre><code>/**
   * Foo
   *
   * @ORM\Table(name="foos", ...)
   * @ORM\Entity
   * @ORM\InheritanceType("JOINED")
   * @ORM\DiscriminatorColumn(name="type", type="string")
   * @ORM\DiscriminatorMap({
   *     "bar" = "Bar",
   *     "buz" = "Buz"
   * })
   */
  abstract class Foo
  {
      ...
  }
  </code></pre>
  
  <p>Since I run the "code first" approach, the database is generated by Doctrine:</p>
  
  <pre><code>$ bin/console doctrine:migrations:diff
  $ bin/console doctrine:migrations:migrate
  </code></pre>
  
  <p>The discriminator column <code>foos.type</code> gets the type <code>VARCHAR(255)</code>. I want it to get an <code>ENUM</code> instead.</p>
  
  <p><strong>How to define the annotation for the entity class for getting an <code>ENUM</code> discriminator?</strong></p>