Final Class Yiisoft\Mailer\MessageSettings

                public function __construct(
    public readonly string|null $charset = null,
    public readonly array|string|null $from = null,
    public readonly array|string|null $addFrom = null,
    public readonly array|string|null $to = null,
    public readonly array|string|null $addTo = null,
    public readonly array|string|null $replyTo = null,
    public readonly array|string|null $addReplyTo = null,
    public readonly array|string|null $cc = null,
    public readonly array|string|null $addCc = null,
    public readonly array|string|null $bcc = null,
    public readonly array|string|null $addBcc = null,
    public readonly string|null $subject = null,
    public readonly DateTimeImmutable|null $date = null,
    public readonly Priority|null $priority = null,
    public readonly string|null $returnPath = null,
    public readonly string|null $sender = null,
    public readonly string|null $textBody = null,
    public readonly string|null $htmlBody = null,
    public readonly array|null $attachments = null,
    public readonly array|null $addAttachments = null,
    public readonly array|null $embeddings = null,
    public readonly array|null $addEmbeddings = null,
    array|null $headers = null,
    array|null $overwriteHeaders = null,
    callable|null $htmlToTextBodyConverter = null,
) {
    $this->headers = HeadersNormalizer::normalize($headers);
    $this->overwriteHeaders = HeadersNormalizer::normalize($overwriteHeaders);
    $this->htmlToTextBodyConverter = $htmlToTextBodyConverter;
}

            

                public function applyTo(MessageInterface $message): MessageInterface
{
    if ($this->charset !== null && $message->getCharset() === null) {
        $message = $message->withCharset($this->charset);
    }
    if ($this->from !== null && $message->getFrom() === null) {
        $message = $message->withFrom($this->from);
    }
    if ($this->addFrom !== null) {
        $message = $message->withAddedFrom($this->addFrom);
    }
    if ($this->to !== null && $message->getTo() === null) {
        $message = $message->withTo($this->to);
    }
    if ($this->addTo !== null) {
        $message = $message->withAddedTo($this->addTo);
    }
    if ($this->replyTo !== null && $message->getReplyTo() === null) {
        $message = $message->withReplyTo($this->replyTo);
    }
    if ($this->addReplyTo !== null) {
        $message = $message->withAddedReplyTo($this->addReplyTo);
    }
    if ($this->cc !== null && $message->getCc() === null) {
        $message = $message->withCc($this->cc);
    }
    if ($this->addCc !== null) {
        $message = $message->withAddedCc($this->addCc);
    }
    if ($this->bcc !== null && $message->getBcc() === null) {
        $message = $message->withBcc($this->bcc);
    }
    if ($this->addBcc !== null) {
        $message = $message->withAddedBcc($this->addBcc);
    }
    if ($this->subject !== null && $message->getSubject() === null) {
        $message = $message->withSubject($this->subject);
    }
    if ($this->date !== null && $message->getDate() === null) {
        $message = $message->withDate($this->date);
    }
    if ($this->priority !== null && $message->getPriority() === null) {
        $message = $message->withPriority($this->priority);
    }
    if ($this->returnPath !== null && $message->getReturnPath() === null) {
        $message = $message->withReturnPath($this->returnPath);
    }
    if ($this->sender !== null && $message->getSender() === null) {
        $message = $message->withSender($this->sender);
    }
    if ($this->textBody !== null && $message->getTextBody() === null) {
        $message = $message->withTextBody($this->textBody);
    }
    if ($this->htmlBody !== null && $message->getHtmlBody() === null) {
        $message = $message->withHtmlBody($this->htmlBody);
    }
    if ($this->attachments !== null && $message->getAttachments() === null) {
        $message = $message->withAttachments(...$this->attachments);
    }
    if ($this->addAttachments !== null) {
        $message = $message->withAddedAttachments(...$this->addAttachments);
    }
    if ($this->embeddings !== null && $message->getEmbeddings() === null) {
        $message = $message->withEmbeddings(...$this->embeddings);
    }
    if ($this->addEmbeddings !== null) {
        $message = $message->withAddedEmbeddings(...$this->addEmbeddings);
    }
    if ($this->headers !== null) {
        $message = $message->withHeaders(
            array_merge($this->headers, $message->getHeaders() ?? [])
        );
    }
    if ($this->overwriteHeaders !== null) {
        foreach ($this->overwriteHeaders as $headerName => $headerValue) {
            $message = $message->withHeader($headerName, $headerValue);
        }
    }
    if ($this->htmlToTextBodyConverter !== null && $message->getTextBody() === null) {
        $html = $message->getHtmlBody();
        if ($html !== null) {
            $message = $message->withTextBody(
                ($this->htmlToTextBodyConverter)($html)
            );
        }
    }
    return $message;
}