Add user_added.ejs email template

This allows us to also send an invitation link to admins
in case the user was not invited already.

src/mail_templates/user_added.ejs

@@ -0,0 +1,22 @@
+<%if (format === 'text') { %>
+
+Dear Admin,
+
+User with name '<%= username %>' (<%= email %>) was added in the Cloudron at <%= fqdn %>.
+
+You are receiving this email because you are an Admin of the Cloudron at <%= fqdn %>.
+
+<% if (inviteLink) { %>
+This user was not invited immediately, he has to get invited manually later, using the "send invite" button in the admin panel.
+To perform any configuration on behalf of the user, please follow the invitation link <%= inviteLink %>
+It allows to setup a temporary password, which the user will be able to override, once he gets invited.
+This link will become invalid as soon as the user was invited.
+<% } %>
+
+Thank you,
+User Manager
+
+<% } else { %>
+
+<% } %>
+