public function __construct(\Planning_Milestone $milestone)
 {
     $this->id = JsonCast::toInt($milestone->getArtifactId());
     $this->label = $milestone->getArtifactTitle();
     $this->last_modified = JsonCast::toDate($milestone->getLastModifiedDate());
     $this->uri = self::ROUTE . '/' . $this->id;
 }