Replace mailjet with mailgun (#180)

lib/plugins/email/mailgun/mailgun.js

@@ -0,0 +1,21 @@
+const Mailgun = require('mailgun-js')
+
+const NAME = 'Mailgun'
+
+function sendMessage ({apiKey, domain, fromEmail, toEmail}, rec) {
+  const mailgun = Mailgun({apiKey, domain})
+
+  const emailData = {
+    from: `Lamassu Server ${fromEmail}`,
+    to: toEmail,
+    subject: rec.email.subject,
+    text: rec.email.body
+  }
+
+  return mailgun.messages().send(emailData)
+}
+
+module.exports = {
+  NAME,
+  sendMessage
+}