Support for certificates with expiration date

[poszu]

Support for certificates with an optional expiration date. A certificate is a scale-encoded combination of the node's ID and (optional) expiration time. If the expiration time is None, the certificate does not expire.

The certifier will create expiring certificates if the expiration duration is set in the config.

[codecov]

Codecov Report

Attention: Patch coverage is 94.89051% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 94.10%. Comparing base (69da0db) to head (9d9a2f2).

Files	Patch %	Lines
certifier/src/certifier.rs	94.69%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #219      +/-   ##
==========================================
+ Coverage   93.89%   94.10%   +0.20%     
==========================================
  Files          26       27       +1     
  Lines        3376     3496     +120     
==========================================
+ Hits         3170     3290     +120     
  Misses        206      206              

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[fasmat]

There is a linter warning in profiler/src/main.rs that maybe can be fixed in this PR as well?

[fasmat]

Maybe a bit late, but we could have gone the route of using actual x509 certificates and then use client authentication (mTLS) against the certifier, would have probably been less implementation effort and made it easier to develop 3rd party tools or alternative implementations.

[poszu]

Could a x509 certificate be only valid for a single nodeID? A certificate should allow for only 1 poet registration per round.

[fasmat]

Yes, a certificate would be for a specific public key until a given expiration date. I don't think the effort to change it now is worth it though.

[poszu]

There is a linter warning in profiler/src/main.rs that maybe can be fixed in this PR as well?

That's already fixed on the main branch :)