Simplify createTransactionBody

[newhoggy]

Changelog

- description: |
    Simplify `createTransactionBody`
# 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

Includes commits from #333 so review that first.

How to trust this PR

Highlight important bits of the PR that will make the review faster. If there are commands the reviewer can run to observe the new behavior, describe them.

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated. See Running tests for more details
• Self-reviewed the diff

[newhoggy]

The focus of this PR is to simplify this function.

The earlier version of this code case matches on sbe and handles each era therein separately resulting in a lot of duplicate code.

The new version of this function instead eliminates the large case expression and instead uses eons allow each feature to determine for themselves if they need to set their values into the TxBody.

[newhoggy]

With this refactoring we can deal with each tx body feature in isolation without duplication.

This can be simplified further in a future PR.

[newhoggy]

modityWith shouldn't be necessary but ghc's type inference isn't quite there.

[newhoggy]

This is just temporary because we need a witness. A future PR will get rid of this.

[newhoggy]

These lenses take witnesses instead of constraints. This can be used in future to simplify code.

[newhoggy]

One of the goals of this PR is to eliminate to need to case match on the era and handle each era separately. Doing away with this case expression vastly reduces code duplication and the potential for error.

[carbolymer]

https://github.com/input-output-hk/cardano-api/pull/333/files#r1368451851

Comments addressed

[carbolymer]

Why do you need >>= here? Why not:

Suggested change

	setMint <-
	caseShelleyToAllegraOrMaryEraOnwards
	(const $ pure id)
	(const $ pure $ L.mintTxBodyL .~ convMintValue apiMintValue)
	sbe
	let setMint =
	caseShelleyToAllegraOrMaryEraOnwards
	(const $ id)
	(const $ L.mintTxBodyL .~ convMintValue apiMintValue)
	sbe

[newhoggy]

This is mostly to make all of the units of code have the same shape rather than have some unit use let and others use <-.

You are right in that the >>= is not needed.