test(filters): cover dev-only detail disclosure in the exception filter

[Mayor-Isaac]

Overview

This PR adds unit tests for the GlobalExceptionFilter's dev-only internal error details disclosure. It exercises both sides of the isDevelopment() branch — asserting details is present when development mode is enabled and absent when disabled — and completes coverage for the isPrismaError and isValidationError type guards, raising branch coverage for the file above 85%.

Related Issue

Closes #

Changes

🧪 Exception Filter Test Coverage

• [ADD] test/unit/global-exception.filter.spec.ts

  • Validation error with ConfigService.isDevelopment() mocked to true asserts details is present in the HTTP response.
  • Validation error with ConfigService.isDevelopment() mocked to false asserts details is absent.
  • isPrismaError covered with a matching Prisma exception and a non-matching plain exception.
  • isValidationError covered with a matching validation exception and a non-matching exception.

• [MODIFY] Test mocking approach

  • Mock ConfigService.isDevelopment() instead of mutating NODE_ENV, avoiding environment leakage between tests.

Verification Results

npm test -- test/unit/global-exception.filter.spec.ts
✅ All tests passed

Branch coverage:
✅ src/common/filters/global-exception.filter.ts > 85% branches
✅ isDevelopment() true → details present
✅ isDevelopment() false → details absent
✅ isPrismaError matching + non-matching covered
✅ isValidationError matching + non-matching covered

Acceptance Criteria	Status
Validation error with isDevelopment() true asserts details present	✅ Added test with mocked isDevelopment() => true
Validation error with isDevelopment() false asserts details absent	✅ Added test with mocked isDevelopment() => false
isPrismaError and isValidationError each covered with matching and non-matching exception	✅ Both type guards tested on both sides
Branch coverage for this file is above 85%	✅ Achieved

Closes #704

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