public function addToTeam(Team $team, $timestamp = null)
{
if (null !== $this->playsIn) {
throw new \InvalidArgumentException('You must remove the current membership before adding a new one');
}
$dt = new \DateTime('NOW', new \DateTimeZone('UTC'));
$time = null !== $timestamp ? $timestamp : $dt->getTimestamp();
$membership = new PlaysInTeam($this, $team, $time);
$this->playsIn = $membership;
$team->addMembership($membership);
}