fix: generate new root ca when it expires

[gruyaume]

Description

Here we generate a new root CA when it expires and we don't revoke certificates created by old CA. In any case, this "revocation" didn't do much as we don't maintain a CRL.

Fixes #239

Checklist:

• [ ] My code follows the style guidelines of this project
• [ ] I have performed a self-review of my own code
• [ ] I have made corresponding changes to the documentation
• [ ] I have added tests that validate the behaviour of the software
• [ ] I validated that new and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules
• [ ] I have bumped the version of the library

[gruyaume]

Blocking this PR as it will be addressed in the context of TLSENG-343

Sure, I'll close it then