code: public function add(Recipient $recipient)
      {
          foreach ($this->recipients as $r) {
              if ($r->getEmail() === $recipient->getEmail()) {
                  $r
                      ->setType($recipient->getType())
                      ->setName($recipient->getName());
  
                  return $this;
              }
          }
  
          $this->recipients[] = $recipient;
  
          return $this;
      }
docs: Adds the recipient.
  
  @param Recipient $recipient
  
  @return $this|RecipientList