<?php

namespace UCP\AbsenceBundle\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity
 */
class Lesson
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    private $id;

    /**
     * @ORM\ManyToOne(targetEntity="User")
     */
    private $professor;

    /**
     * @ORM\Column(type="string")
     */
    private $label;

    /**
     * @ORM\Column(type="datetime")
     */
    private $start;

    /**
     * @ORM\Column(type="datetime")
     */
    private $end;
}

<?php

namespace UCP\AbsenceBundle\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity
 */
class Lesson
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    private $id;

    /**
     * @ORM\ManyToOne(targetEntity="User")
     */
    private $professor;

    /**
     * @ORM\Column(type="string")
     */
    private $label;

    /**
     * @ORM\Column(type="datetime")
     */
    private $start;

    /**
     * @ORM\Column(type="datetime")
     */
    private $end;

    /**
     * @ORM\Column(type="string")
     */
    private $eventId;
}

Add eventId to lesson to keep track of related calendar event
Add eventId to lesson to keep track of related calendar event
