/**
  * @return \yii\db\ActiveQuery
  */
 public function getCoupon()
 {
     return $this->hasOne(Coupon::className(), ['id' => 'coupon_id']);
 }
 /**
  * @return \yii\db\ActiveQuery
  */
 public function getCoupons()
 {
     return $this->hasMany(Coupon::className(), ['id' => 'coupon_id'])->viaTable('Participant_has_coupon', ['Participant_id' => 'id']);
 }