Don't export coerceKeyRole, export RewardAccount

[smelc]

Changelog

- description: |
    Don't export the ledger's `coerceKeyRole` function anymore, export RewardAccount
# 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
  # - refactoring    # QoL changes
  # - 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 Augment of query spo-stake-distribution to include the DRep delegation choices of the Pool's rewards accounts cardano-cli#990
• This is the datatype RewardAccount that is being exported
• The export of coerceKeyRole is no longer necessary for solving [FEATURE] - Update cardano-cli conway query spo-stake-distribution cardano-cli#911, which is good; because @Jimbo4350 had concerned about it (on Slack). I must say I readied Export HasKeyRole's coerceKeyRole function #699 too fast.

Not marking this one as breaking, because it actually reverts #699. Since there was no release since 699, overall it's not going to be a breaking change.

How to trust this PR

The new export only concerns a data structure, nothing controversial

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• Self-reviewed the diff

[palas]

Looks good, but it does seem breaking. It would need to be noted in the changelog

[palas]

This does look breaking: It would be exporting coerceKeyRole, if I understand correctly, I may be wrong.

[palas]

Ah, you already said. But I mean the breaking tag should be uncommented

[smelc]

@palas> it's not breaking, because this bit is the revert of #699. And since we didn't release between this PR and 699, the net effect of this PR on the next release is the additional export of RewardAccount.