Review chain helpers - Closes #3035

[diego-G]

Review checklist

• The PR resolves Review chain/helpers/ content #3035
• All new code is covered with unit tests
• All new code was formatted with Prettier
• Linting passes
• Tests pass
• Commit messages follow the commit guidelines
• Documentation has been added/updated

[shuse2]

LGTM just small question

[MaciejBaj]

Nice, good work so far.
What's missing:

helpers/index.js is outdated and can be removed
helpers/diff.js - maybe remove or the name should at least describe the operation on votes
helpers/transaction_types - I think should be moved to constants
helpers/z_schema is now duplicated with framework/src/controller/helpers/validator, we should use the formats defined there and only import them into z_schema

[2snEM6]

@diego-G, regarding @MaciejBaj comment, let me know if you do something with helpers/transaction_types.js, maybe it solves code duplication on HTTP API too.

[shuse2]

Also, I realised that slot.js is left behind in the helper, can we move it to logic or to appropriate round file?

[diego-G]

@shuse2 helper/slots.js is used in many places. There are several logics, several submodules and two api controllers that make use of that util. I reckon it should be kept as a helper.

[shuse2]

As discussed, please move the slot file to the logic folder for now

[diego-G]

@shuse2 due to several hurdles and the current PR's size, I decide to open an independent issue to tackle your suggestion about helper slots. #3070