[5.6] Allow to set plain HTML in mails

[abellion]

We use MJML as a template engine for our mails. It returns us plain HTML, so having this PR merged would make easier setting plain HTML to mails (we use a blade "wrapper" today as a workaround).

[taylorotwell]

Can you explain more what you mean by "plain" HTML? Doesn't the mailer already allow you to send views? Or you mean there is no view at all?

[abellion]

Yeah there is no view at all.

[taylorotwell]

I'm wondering if it makes sense to do this. AFAIK it's good practice to always include a text part:

if (isset($this->html)) {
    return array_filter([
        'html' => new HtmlString($this->html),
        'text' => isset($this->textView) ? $this->textView : null,
    ]);
}

[abellion]

Yes you're right, I've updated the html() method of the Mailable class.

Should I also update the one from the Mailer class ?
The signature could looks like this :

public function html($html, $callback, $plain = null);

What do you think ? The raw and send methods don't give this possibility, so maybe it's unnecessary.

[taylorotwell]

I don't think it's necessary on Mailer since I could always just call Mail::send(['html' => foo, 'text' => bar]) already. So it's already possible there.

[abellion]

Makes sense.