FINERACT-1474: Remove hard-coded constants from ExternalCreditBureauTest

[debcodes076]

Description

This PR addresses Issue 1474 by refactoring the ExternalCreditBureauIntegrationWritePlatformServiceImplTest.java file and its implementation to remove hard-coded strings and magic numbers.

Changes Made

• Renamed the service and test classes to be vendor-neutral (e.g., ExternalCreditBureau...).
• Introduced private static final constants for CREDIT_BUREAU_ID, TEST_USERNAME, TEST_PASSWORD, and TEST_URL.
• Updated the setup() method and all @Test cases to utilize these constants.
• Verified that the refactor does not break functionality by running the local test suite.

Verification

• Ran the test command: ./gradlew :fineract-provider:test --tests "org.apache.fineract.infrastructure.creditbureau.service.ExternalCreditBureauIntegrationWritePlatformServiceImplTest"
• Result: BUILD SUCCESSFUL

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Checklist

• Write the commit message as per guidelines
• Acknowledge that the build passes locally
• Follow coding conventions

This is my first contribution to Apache Fineract as part of my GSoC 2026 preparation.

[IOhacker]

Hello, "ThitsaWorks" seems to be non neutral, it must be removed or replaced.

[debcodes076]

Hello, "ThitsaWorks" seems to be non neutral, it must be removed or replaced.

thank you for the feedback! i've refactored the code to replace all "Thitsaworks.." references with "ExternalCredit..." (including file name, classnames, method names) to ensure vendor neutrality.