MPT-14933 E2E for notifications/contacts

[albertsola]

Summary by CodeRabbit

• Tests
  • Added comprehensive end-to-end tests for contact operations: create, retrieve, list, update, delete, block/unblock, and not-found handling.
  • Extended coverage for both synchronous and asynchronous workflows; test modules marked as flaky where applicable.
  • Added fixtures for contact data, created contact (sync/async), created contact ID, and an invalid contact ID for error scenarios.

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