test(integrations): Add unit tests for Integrations API client

[vikramlc-cognite]

Summary

Adds unit tests (mocked HTTP) for IntegrationsAPI's CRUD methods and the Tasks, Errors, Config, and Actions sub-APIs implemented in #2820, plus retry-idempotency coverage in test_api_client.py.

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that changes existing behavior)
• Refactor (no functional change)
• Documentation update
• Chore / tooling / CI

What changed

• tests/tests_unit/test_api/test_integrations/test_integrations.py — list/create/retrieve/update/delete, including the cdf-version beta header assertion.
• test_actions.py, test_config.py, test_errors.py, test_tasks.py — one file per sub-API, covering request shape (method/URL/body) and response parsing, plus the validation-error paths (list_history requiring external_id when task_name is given; sync requiring include_errors or include_task_updates; errors.list requiring external_id when task is given).
• test_api_client.py — added TestRetryableEndpoints cases for integrations, integrations/config, integrations/actions*.

Why it changed

• Related issue: EDG-827
• Related docs / discussion: follows the same httpx_mock + get_url()/jsgz_load() pattern used by the existing simulators test suite.

What to focus on during review

• These tests exercise the API strictly through cognite_client.integrations.* / async_client.integrations.* (never by instantiating the sub-API classes directly), matching how every other API module in this SDK is tested.
• The validation-error tests (ValueError on missing external_id/include_errors/include_task_updates combinations) are the only behavior-defining tests here — everything else is round-trip request/response verification.

Test evidence

• pytest tests/tests_unit/ -q → 6,669 passed, 8 failed (pre-existing, unrelated: missing geopandas/sympy in the local dev environment, same failures present on master), 6 skipped
• Confirmed this branch reconstructs the original (unsplit) integrations-part2-core-api branch byte-for-byte (git diff against it is empty)
• ruff check / ruff format --check → clean

Risks and unknowns

• None beyond what's already covered in feat(integrations): Implement Integrations API client (CRUD + sub-resources) #2820 — this PR is pure test coverage, no production code changes.

Rollout and rollback

• N/A — test-only change, no runtime behavior affected. Revert is a straight revert of this commit.

Checklist

• Self-reviewed the diff
• Tests added or updated (or N/A with reason)
• Docs updated (or N/A) — N/A, test-only change
• No secrets, credentials, or PII committed
• Breaking changes called out above and communicated to affected teams — N/A, no breaking changes

[gemini-code-assist]

Code Review

This pull request adds comprehensive unit tests for the integrations API, covering actions, configuration, errors, integrations, and tasks. It also updates the API client tests to register the new integration endpoints as retryable or non-retryable. I have no feedback to provide as there are no review comments.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (integrations-part2.1-core-api-impl@33f7b9a). Learn more about missing BASE report.

Additional details and impacted files

@@                          Coverage Diff                          @@
##             integrations-part2.1-core-api-impl    #2821   +/-   ##
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  Coverage                                      ?   93.24%           
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  Files                                         ?      538           
  Lines                                         ?    54509           
  Branches                                      ?        0           
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  Hits                                          ?    50826           
  Misses                                        ?     3683           
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Files with missing lines	Coverage Δ
...ts_unit/test_api/test_integrations/test_actions.py	100.00% <100.00%> (ø)
...sts_unit/test_api/test_integrations/test_config.py	100.00% <100.00%> (ø)
...sts_unit/test_api/test_integrations/test_errors.py	100.00% <100.00%> (ø)
...it/test_api/test_integrations/test_integrations.py	100.00% <100.00%> (ø)
...ests_unit/test_api/test_integrations/test_tasks.py	100.00% <100.00%> (ø)
tests/tests_unit/test_api_client.py	99.72% <ø> (ø)

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