Implement BigNumber library to do all numerical processing wrapped in a Mojaloop Number Library

[elnyry-sam-k]

Goal:

As a Hub Operator
I want to support processing of amounts as decimals during internal processing while supporting the maximum precision as specified in the API Definition along with enforcing precision based on currency
so that requests with input values for amounts that only conform to the conditions based on currency are accepted and the others are rejected (via error callbacks) and the 'zero sum' of the system is maintained

This specific story is for the Mojaloop Decimal Library

Tasks:

• Present options for the library after investigation, for review
  • bignumbers.js library selected as number library
  • create basic functionality as a POC i.e (add, subtract, multiply, divide)
  • review POC and validate that the selected library fulfils requirements
• Mojaloop Numbers Library implementation that uses decimal processing of amounts/ numbers
  • Refactor to MLNumber [@ggrg]
• Add to applicable APIs for implementation and testing
  • central-ledger [@ggrg]
  • central-settlements [@ggrg]
  • quoting-service [@ggrg]
  • Optionally CEP* [@ggrg]
• Validation for Golden path tests
• Documentation for usage

Acceptance Criteria:

• Unit Tests pass
• The DB supports max precision of 4 digits as specified in the API Definition v1.0
• The Mojaloop Decimal Library is made available to be used by central services for numbers (amount) processing internally

Pull Requests:

• Initial commit for story #953 ml-number#1
• hotfix/Refactor to ML Number ml-number#3
• feature/952 Implement ML Number library central-ledger#426
• hotfix/Refactor to uppercase L in ML Number central-ledger#427
• feature/952 Implement ML Number Library central-settlement#149
• feature/952 Implement ML Number library quoting-service#54
• Feature/952 Implement ML Number Library central-event-processor#71

Follow-up:

Future Roadmap:
We should consider using this library to include ISO Currency enums, validation, and also config for MLNumbers based on currency config

Dependencies:

• N/A

Accountability:

• Owner: @rmothilal
• QA/Review: @rmothilal @mdebarros