Add RevokedAt field to OriginCACertificate

[player-two]

Description

Given a cert ID, I want to know if it has been revoked or not. The list call already filters out revoked certs, but that could require multiple calls to traverse pages when looking for the absence of an ID.

This field was originally added in #387 and pulled out (guessing unintentionally), which is fine because it wasn't very obvious nor related to the rest of that change.

Has your change been tested?

Just via a small script that prints the struct after revoking and re-fetching by the ID

Types of changes

What sort of change does your code introduce/modify?

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[patryk]

Ops! I didn't notice you added new field, sorry!

[player-two]

No problem at all!