Make mail transports pluggable and move integrations to plugins

- Postmark: https://github.com/kanboard/plugin-postmark
- Mailgun: https://github.com/kanboard/plugin-mailgun
- Sendgrid: https://github.com/kanboard/plugin-sendgrid

app/Core/Mail/Transport/Mail.php

@@ -0,0 +1,57 @@
+<?php
+
+namespace Kanboard\Core\Mail\Transport;
+
+use Swift_Message;
+use Swift_Mailer;
+use Swift_MailTransport;
+use Swift_TransportException;
+use Kanboard\Core\Base;
+use Kanboard\Core\Mail\ClientInterface;
+
+/**
+ * PHP Mail Handler
+ *
+ * @package  transport
+ * @author   Frederic Guillot
+ */
+class Mail extends Base implements ClientInterface
+{
+    /**
+     * Send a HTML email
+     *
+     * @access public
+     * @param  string  $email
+     * @param  string  $name
+     * @param  string  $subject
+     * @param  string  $html
+     * @param  string  $author
+     */
+    public function sendEmail($email, $name, $subject, $html, $author)
+    {
+        try {
+
+            $message = Swift_Message::newInstance()
+                ->setSubject($subject)
+                ->setFrom(array(MAIL_FROM => $author))
+                ->setBody($html, 'text/html')
+                ->setTo(array($email => $name));
+
+            Swift_Mailer::newInstance($this->getTransport())->send($message);
+        }
+        catch (Swift_TransportException $e) {
+            $this->logger->error($e->getMessage());
+        }
+    }
+
+    /**
+     * Get SwiftMailer transport
+     *
+     * @access protected
+     * @return \Swift_Transport
+     */
+    protected function getTransport()
+    {
+        return Swift_MailTransport::newInstance();
+    }
+}

app/Core/Mail/Transport/Sendmail.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace Kanboard\Core\Mail\Transport;
+
+use Swift_SendmailTransport;
+
+/**
+ * PHP Mail Handler
+ *
+ * @package  transport
+ * @author   Frederic Guillot
+ */
+class Sendmail extends Mail
+{
+    /**
+     * Get SwiftMailer transport
+     *
+     * @access protected
+     * @return \Swift_Transport
+     */
+    protected function getTransport()
+    {
+        return Swift_SendmailTransport::newInstance(MAIL_SENDMAIL_COMMAND);
+    }
+}

app/Core/Mail/Transport/Smtp.php

@@ -0,0 +1,30 @@
+<?php
+
+namespace Kanboard\Core\Mail\Transport;
+
+use Swift_SmtpTransport;
+
+/**
+ * PHP Mail Handler
+ *
+ * @package  transport
+ * @author   Frederic Guillot
+ */
+class Smtp extends Mail
+{
+    /**
+     * Get SwiftMailer transport
+     *
+     * @access protected
+     * @return \Swift_Transport
+     */
+    protected function getTransport()
+    {
+        $transport = Swift_SmtpTransport::newInstance(MAIL_SMTP_HOSTNAME, MAIL_SMTP_PORT);
+        $transport->setUsername(MAIL_SMTP_USERNAME);
+        $transport->setPassword(MAIL_SMTP_PASSWORD);
+        $transport->setEncryption(MAIL_SMTP_ENCRYPTION);
+
+        return $transport;
+    }
+}