[9.x] Added conditional lines to MailMessage

[shino47]

Currently, If we need to add a line to a MailMessage based on a condition, we have to do something like this:

public function toMail($notifiable)
{
    $message = new MailMessage();
    $message->greeting('Hello there!');
    $message->line('Your order has been canceled');
    if ($this->amount > 0) {
        $message->line("The refunded amount is {$this->amount}");
    }
    $message->line('...');
    return $message;
}

With these methods, we can do:

public function toMail($notifiable)
{
    return (new MailMessage)
        ->greeting('Hello there!')
        ->line('Your order has been canceled')
        ->lineIf($this->amount > 0, "The refunded amount is {$this->amount}")
        ->line('...');
}

Which looks similar to the docs.

[mateusjatenee]

I wonder if using the Conditionable trait isn't a better approach here — that'd allow us to call any methods based on a condition.

Edit: nevermind, just saw that MailMessage uses Conditionable.