Unit test cases for services (#1511)

* Unit test cases for services

Signed-off-by: Mohan Lakshmaiah <[email protected]>

* fix: improve unit tests for services

- Remove unused imports (utc_now, ensure_timezone_aware)
- Replace problematic global joinedload mock with test-scoped decorator
- Fix duplicate test function names (test_trace_tool_invocation_success,
  test_trace_a2a_request_success)
- Replace weak assertions (assert True, or True) with meaningful checks
- Fix whitespace and formatting issues per flake8
- Add missing newlines at end of files

Signed-off-by: Mihai Criveti <[email protected]>

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Signed-off-by: Mohan Lakshmaiah <[email protected]>
Signed-off-by: Mihai Criveti <[email protected]>
Co-authored-by: Mohan Lakshmaiah <[email protected]>
Co-authored-by: Mihai Criveti <[email protected]>

Author: 3 people