Added E2E integration tests

[srivanimuddineni]

1. Created NotificationPcrE2EIntegrationTest :
   1. test_document_retrieval_success
   2. test_document_retrieval_failure (Added comments which can be removed after QA handover)
2. Tidy up stubs folder structure
3. Added is a WireMock transformer - response-template to dynamically generate port..
4. The E2E test is simplified to one core assertion - subscriber can retrieve the pdf
5. consolidated setup and helpers, callback wiremock, moving common stubs to the base, ssl configuration for callback
   url.
6. added test profile for timeout variables
7. Resolved review comments for folder naming and constants reusability
8. SSLTrustingRestTemplateConfig class trusts WireMock’s self-signed https certificate for e2ecallback tests. It is only used for testing and not in production.
9. Removed CallbackUrlDeliveryException; failures/timeouts are handled by the global exception handler.
   ConditionTimeoutException → 504 with "Material metadata not ready".
   CallbackService retries on failure; timeout exceptions propagate globally.
10. Moved WireMock callback stubs to CallbackStub and reused in E2E tests.
11. Added Awaitility to CallbackService
12. Updated test cases accordingly
13. codeql rule by pass specific to tests

[coling01]

Looks great ... think we can improve it a little but good start :)

[samirgarg]

Thanks for the great work. Some minor comments to make it even better