[5.3] Setting email priority/importance with Mailable

[KKSzymanowski]

From what I know the only way to set email priority is to register a callback in the build method:

class NewInquiry extends Mailable
{

    use Queueable, SerializesModels;

    public function build()
    {
        return $this->subject('New inquiry')
            ->withSwiftMessage(function($message) {
                $message->setPriority(1);
            })
            ->view('emails.inquiry.new');
    }
}

Am I correct?

Can I make a PR of a fluent method setting this priority? Like that:

public function priority($level)
{
    $this->callbacks[] = function($message) use ($level) {
        $message->setPriority($level);
    };

    return $this;
}