[Feature]: certificate chain validator

[bradh11]

Pre-flight checklist

• I have searched existing issues to make sure this feature hasn't been requested
• I have read the documentation to ensure this feature doesn't already exist
• This feature aligns with the project's goals and scope

Problem Statement

I’m always frustrated when an intermediary or root certificate change causes an issue with my host certificate.

Proposed Solution

I would like certmonitor to be able to fetch the whole cert chain and validate the details of each.

Feature Category

New validator

Use Case

The validator should

1. Fetch the whole cert chain
2. get details for intermediary or certificate authority
3. Validate against missing chain members
4. validate chain members are all valid (not expired, not revoked, etc…)

Implementation Ideas

No response

Code Examples

Alternatives Considered

No response

Priority

Medium - Would be helpful

Contribution

• I would be willing to implement this feature
• I would be willing to write tests for this feature
• I would be willing to write documentation for this feature
• I would be willing to help with code review

Additional Context

No response