notifications: per user email prefs

src/mail_templates/backup_failed.ejs

@@ -13,8 +13,11 @@ Cloudron failed to create a complete backup. Please see the logs at <%= logUrl %
 
 Powered by https://cloudron.io
 
+Don't want such mails? Change your notification preferences at <%= notificationsUrl %>
+
 Sent at: <%= new Date().toUTCString() %>
 
+
 <% } else { %>
 
 <% } %>

src/mail_templates/certificate_renewal_error.ejs

@@ -23,6 +23,8 @@ The error was:
 
 Powered by https://cloudron.io
 
+Don't want such mails? Change your notification preferences at <%= notificationsUrl %>
+
 Sent at: <%= new Date().toUTCString() %>
 
 <% } else { %>