Add vegetarian dinner option

Change-Id: Ibcda53e07467957f12ccbaf5bc8dc02b9944365f
diff --git a/User.php b/User.php
index 790af5a..aa7357c 100644
--- a/User.php
+++ b/User.php
@@ -25,6 +25,7 @@
     public $participation_confirmed_at;
     public bool $student;
     public bool $conference_dinner;
+    public bool $vegetarian_dinner;
     public $registered_at;
     public bool $earlybird_registration;
     public $lunch_day_1;
@@ -56,6 +57,7 @@
         $this->participation_confirmed_at = "";
         $this->student = false;
         $this->conference_dinner = false;
+        $this->vegetarian_dinner = false;
         $this->registered_at = date("Y-m-d H:i:s") . "UTC";
         $this->earlybird_registration = false;
         $this->total_due = 0.0;