class Admin extends BaseUser
{
    /**
     * @ORM\Id()
     * @ORM\Column(name="idAdmin", type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    protected $id;

    /**
     * @var string
     * @ORM\Column(type="string", length=255, nullable=true, options={"default":NULL})
     */
    protected $style;

    /**
     * @ORM\ManyToMany(targetEntity="AdminBundle\Entity\AdminGroup")
     * @ORM\JoinTable(
     *     name="admin_has_group",
     *     joinColumns={
     *         @ORM\JoinColumn(name="idAdmin", referencedColumnName="idAdmin")
     *     },
     *     inverseJoinColumns={
     *         @ORM\JoinColumn(name="idGroup", referencedColumnName="idGroup")
     *     }
     * )
     */
    protected $groups;

    /**
     * Admin constructor.
     */
    public function __construct()
    {
        parent::__construct();
        $this->groups = new ArrayCollection();
    }

    /**
     * @return string
     */
    public function getStyle()
    {
        return $this->style;
    }

    /**
     * @param string $style
     * @return Admin
     */
    public function setStyle($style)
    {
        $this->style = $style;

        return $this;
    }

    /**
     * @param ArrayCollection
     *
     * @return Admin
     */
    public function setGroups($groups)
    {

        $this->groups = $groups;

        return $this;
    }

    /**
     * @return ArrayCollection
     */
    public function getGroups()
    {
        return $this->groups;
    }

    /**
     * @param GroupInterface $group
     *
     * @return Admin
     */
    public function addGroup(GroupInterface $group)
    {
        if (empty($this->getGroups())) {
            $this->groups = new ArrayCollection();
        }

        if (!$this->getGroups()->contains($group)) {
            $this->getGroups()->add($group);
        }

        return $this;
    }

    /**
     * @param string $name
     *
     * @return bool
     */
    public function hasGroup($name="") {
        dump($name);
        if (!empty($name)) {
            return parent::hasGroup($name);
        }
        return false;
    }
}

--------------------------------------------------------------------------------

class AdminGroup extends BaseGroup
{
    /**
     * @var int
     * @ORM\Id
     * @ORM\Column(name="idGroup", type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    protected $id;

    /**
     * Group constructor.
     *
     * @param string $name
     * @param array  $roles
     */
    public function __construct($name = '', $roles = array())
    {
        parent::__construct($name, $roles);
    }
}

--------------------------------------------------------------------------------

    public function newAction(Request $request)
    {
        $em    = $this->getDoctrine()->getManager();
        $admin = new Admin();
        $form  = $this->buildForm($admin, true);

        $form->handleRequest($request);
        if ($form->isSubmitted() && $form->isValid()) {

            /** @var Admin $admin */
            $admin = $form->getData();

            $admin->setEmail($admin->getUsername());
            $admin->setEnabled(true);

            $em->persist($admin);
            $em->flush();

            return $this->redirectToRoute('backend_admin_list');
        }

        return $this->render(
            'edit.html.twig', [
            'form' => $form->createView(),
        ]);

    }

    public function editAction($id, Request $request)
    {
        $em        = $this->getDoctrine()->getManager();
        $admin     = $this->getDoctrine()->getRepository(Admin::class)->find($id);
        $form      = $this->buildForm($admin);

        $form->handleRequest($request);
        if ($form->isSubmitted() && $form->isValid()) {

            /** @var Admin $admin */
            $admin = $form->getData();

            $em->persist($admin);
            $em->flush();

            return $this->redirectToRoute('index');
        }

        return $this->render(
            'edit.html.twig', [
            'form' => $form->createView(),
        ]);
    }

    protected function buildForm(Admin $admin)
    {
        return $this->createFormBuilder($admin)
            ->add("username", TextType::class, [
                'required' => true,
            ])
            ->add('plainPassword', PasswordType::class, [
                'label'    => 'Passwort',
                'required' => true,
            ])
            ->add(
                'style', ChoiceType::class, [
                'required' => false,
                'choices'  => [
                    'System'   => '',
                    'AdminLTE' => 'adminlte',
                ],
            ])
            ->add('groups', EntityType::class, [
                'class'        => AdminGroup::class,
                'multiple'     => true,
                'choice_label' => 'name',
            ])
            ->add('save', SubmitType::class, ['label' => 'Save'])
            ->getForm();
    }