app/views/user_mailer/send_invitation.html.erb
<html>
<head>
<meta content='text/html; charset=UTF-8' http-equiv='Content-Type' />
</head>
<body>
<h2>Welcome to the American Parliamentary Debate Society!</h2>
<p>
Your invitation code is <%= puts "the invitation code is" %><%= @code %><br>
</p>
<p>
<!-- TODO: need to be updated later-->
Please sign up on <a href="https://cs169-apds.herokuapp.com/users/sign_up">the site</a> with this code. Please contact us if you have questions or concerns.
</p>
<p>Thanks for joining and have a great day!</p>
<p>Best,<br>The American Parliamentary Debate Society</p>
</body>
</html>