Central-Settlement: Refactor handlers model and domain to align with the OSS standards and architecture

[vgenev]

Goal:

As a Mojaloop Developer

I want to Ensure that all the handlers have clearly separated business logic (domain) from data access (model), use enums from central-services-shared library and expose only service API endpoints

so that central-settlement service follows OSS standards for code structure and separation of concerns

Acceptance Criteria:

• Service Domain layer contains all logic required to process the request from a functional perspective
• Model layer cares only for database access
• All constants are loaded from config or central-services-shared library
• Handlers expose only /health and /metrics api
• Rename the transferSettlement handler to grossSettlement handler
• Rename the settlementWindow handler to deferredSettlement handler

Complexity: Low

Uncertainty: Low

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Tasks:

• Move all business logic out of the model to domain layer
• align both the client.id and group.id to match the name of the settlement handler
• use ENUMS instead of 'GROS, 'SETTLED' and others if any
• expose only /health and /metric operations on handlers APIs - /metric is not available in the whole service atm
• Rename the transferSettlement handler to grossSettlement handler
• Rename the settlementWindow handler to deferredSettlement handler
• move out configurations from source to config file: Feature/#1945 cgs merge central-settlement#338 (comment)

Done

• Acceptance Criteria pass
• Designs are up-to date
• Unit Tests pass
• Integration Tests pass
• Code Style & Coverage meets standards
• Changes made to config (default.json) are broadcast to team and follow-up tasks added to update helm charts and other deployment config.
• TBD

Pull Requests:

• feat: #2057 refactoring central-settlement#347

Follow-up:

• N/A

Dependencies:

• N/A

Accountability:

• Owner: TBC
• QA/Review: TBC