Add WithCheckpointVerifier to tessera.StorageOptions for parsing checkpoints

[roger2hk]

#21

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 15 lines in your changes missing coverage. Please review.

Project coverage is 32.67%. Comparing base (46ec9c2) to head (0201b00).
Report is 7 commits behind head on main.

Files	Patch %	Lines
cmd/example-mysql/main.go	0.00%	7 Missing ⚠️
log.go	0.00%	7 Missing ⚠️
cmd/example-gcp/main.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #83      +/-   ##
==========================================
- Coverage   35.80%   32.67%   -3.13%     
==========================================
  Files          16       18       +2     
  Lines        1363     1469     +106     
==========================================
- Hits          488      480       -8     
- Misses        801      917     +116     
+ Partials       74       72       -2     

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[AlCutter]

Just a thought, would it make sense to roll this into the existing WithCheckpointSigner() option?

The existing storage implementations don't need a verifier since they store state internally and just "render" checkpoint from that so never need to verify it, but if there will be other patterns where this isn't case (POSIX too, presumably?) then it'd probably make sense to pop signer & verifier in the same option; it'll avoid bugs where someone passes a signer but not a verifier, and then they only find out when their binary crashes when it tries to integrate.

[roger2hk]

Just a thought, would it make sense to roll this into the existing WithCheckpointSigner() option?

The existing storage implementations don't need a verifier since they store state internally and just "render" checkpoint from that so never need to verify it, but if there will be other patterns where this isn't case (POSIX too, presumably?) then it'd probably make sense to pop signer & verifier in the same option; it'll avoid bugs where someone passes a signer but not a verifier, and then they only find out when their binary crashes when it tries to integrate.

Good point. I have refactored the WithCheckpointSigner to WithCheckpointSignerVerifier.