lib/grape_token_auth/mail/messages/confirmation/confirmation.html.erb
<!DOCTYPE html>
<html>
<head>
<meta content='text/html; charset=UTF-8' http-equiv='Content-Type' />
</head>
<body>
<h1>Email Confirmation</h1>
<p>Hello,</p>
<p>To activate your account please confirm your email by clicking the link below:</p>
<a href="<%= confirmation_link %>"><%= confirmation_link %></a>
<p>If you did not submit this request, please ignore this email</p>
</body>
</html>