Laravel - Notifications - Formatting Slack Notifications

If a notification supports being sent as a Slack message, you should define a toSlack method on the notification class. This method will receive a $notifiable entity and should return an Illuminate\Notifications\Messages\SlackMessage instance. Slack messages may contain text content as well as an "attachment" that formats additional text or an array of fields. Let's take a look at a basic toSlack example:

     * Get the Slack representation of the notification.
     * @param  mixed  $notifiable
     * @return \Illuminate\Notifications\Messages\SlackMessage
    public function toSlack($notifiable)
        return (new SlackMessage)
                    ->content('One of your invoices has been paid!');