Email reminders should give certificate serial numbers

[paulehoffman]

Summary:

Automated email saying "Your certificate (or certificates) for the names listed below will expire" should include the certificate's serial number so that the recipient can check that it's an old cert expiring (fine) and not the current one (disaster).

Steps to reproduce:

This is a feature enhancement request, not a bug report.

Expected result:

This is a feature enhancement request, not a bug report.

Actual result:

This is a feature enhancement request, not a bug report.

Additional details:

N/A