FINERACT-GSOC: Modernize UserHelper and RolesHelper with Fineract-Client

[Avtansh88]

## Description

This PR is a Proof of Concept (PoC) for my GSoC 2026 proposal: "Modernizing Integration Tests with Fineract-Client".

Key Changes:

->UserHelper.java: Refactored legacy RestAssured methods to use type-safe Fineract-Client (Feign).

->RolesHelper.java: Introduced a modern, parameter-less createRole() method to resolve inter-helper dependencies and ensure backward compatibility.

->Type Safety: Replaced manual JSON string building with OpenAPI models like PostUsersRequest and PutUsersUserIdRequest.

->Code Cleanup: Removed redundant RequestSpecification and ResponseSpecification from modernized method signatures.

Checklist

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[vidakovic]

No proper Jira ticket referenced. Is this a problem we have identified or a spontaneous improvement? In short: no Jira ticket, no PR. Please provide a ticket and format the PR title according to the rules ("FINERACT-1234: Some title here"), thanks.

[Avtansh88]

Hi @vidakovic, thanks for the guidance.I've already requested a Jira account to create the formal ticket for this improvement. It might take a couple of days for approval. Once it's active, I'll link the ticket here and update the PR title accordingly. In the meantime, I'm also working on modernizing other helpers like RolesHelper to ensure consistency. Thanks for your patience.