Subscribe to certificates

In sprinter, one can add certificates to have a custom domain or for security reasons. A certificate can expire. When this happens without having another certificate, an app of integration will be unavailable until there is a new valid certificate. This could take hours to weeks (for government certificatie). Therefore:

• I want an e-mail when a certificate will expire, x-time before it gets expired.
• I want to be able to subscribe other e-mail adresses to subscribe to this notification