DRep extended key: add CastVerificationKeyRole

[smelc]

Changelog

- description: |
    DRep extended key: add CastVerificationKeyRole
# uncomment types applicable to the change:
  type:
  # - feature        # introduces a new feature
  # - breaking       # the API has changed in a breaking way
  - compatible     # the API has changed but is non-breaking
  # - optimisation   # measurable performance improvements
  # - improvement    # QoL changes e.g. refactoring
  # - bugfix         # fixes a defect
  # - test           # fixes/modifies tests
  # - maintenance    # not directly related to the code
  # - release        # related to a new release preparation
  # - documentation  # change in code docs, haddocks...

Context

Required for IntersectMBO/cardano-cli#377. Should have been part of #320 but somehow I lost this part during my local rebases 🙃

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• The change log section in the PR description has been filled in
• NA New tests are added if needed and existing tests are updated. These may include:
  • golden tests
  • property tests
  • round trip tests
  • integration tests
    See Running tests for more details
• NA The version bounds in .cabal files are updated
• CI passes. See note on CI. The following CI checks are required:
  • Code is linted with hlint. See .github/workflows/check-hlint.yml to get the hlint version
  • Code is formatted with stylish-haskell. See .github/workflows/stylish-haskell.yml to get the stylish-haskell version
  • Code builds on Linux, MacOS and Windows for ghc-8.10.7 and ghc-9.2.7
• Self-reviewed the diff

[carlhammann]

I get that rawDeserialiseVerKeyDSIGN fails if psbFromByteStringCheck (which is a length check) fails. But the eras I don't understand.

Maybe the message should also say something about extended vs. non-extended DRep keys?

[Jimbo4350]

The error message is definitely a copy-paste. You will need to go code spelunking to figure out a sensible error message.

[smelc]

Indeed it's a copy-paste, which I assumed safe since all other instances of CastVerificationKeyRole do the same.

@carlhammann> I did disambiguate the error message to mention DRep though. Could make our life easier to debug in the future 👍

Since you approved @Jimbo4350, I'm assuming this is good to go, and so I'm not digging into more details.