FINERACT-2116: Add validation integration tests for Credit Bureau Configuration APIs

[DeathGun44]

Description

This PR adds validation integration tests for Credit Bureau Configuration APIs (FINERACT-2116).

Tests cover:

• Credit Bureau Configuration: missing/blank/exceeding length for configkey, value, description
• Organisation Credit Bureau: missing/blank/exceeding length for alias
• Loan Product Mapping: missing loanProductId, isCreditcheckMandatory, skipCreditcheckInFailure, stalePeriod

Important

Dependency: This PR includes a test for missing loanProductId validation which will fail until #5457 is merged. That PR fixes the NPE that causes a 500 error instead of 400 validation error.

Checklist

• Write the commit message as per our guidelines
• Acknowledge that we will not review PRs that are not passing the build ("green")
• Create/update unit or integration tests for verifying the changes made
• Follow our coding conventions
• Add required Swagger annotation and update API documentation at fineract-provider/src/main/resources/static/legacy-docs/apiLive.htm with details of any API changes
• This PR must not be a "code dump"