various notification fixes

src/mail_templates/certificate_renewal_error-text.ejs

@@ -0,0 +1,27 @@
+Dear Cloudron Admin,
+
+The certificate for <%= domain %> could not be renewed.
+
+The Cloudron will attempt to renew the certificate every 12 hours
+until the certificate expires (at which point it will switch to
+using the fallback certificate).
+
+See https://docs.cloudron.io/troubleshooting/#certificates to
+double check if your server is configured correctly to obtain certificates
+via Let's Encrypt.
+
+The error was:
+
+-------------------------------------
+
+<%- message %>
+
+-------------------------------------
+
+
+Powered by https://cloudron.io
+
+Don't want such mails? Change your notification preferences at <%= notificationsUrl %>
+
+Sent at: <%= new Date().toUTCString() %>
+