fix: no-op global client for blank api key

[marandaneto]

💡 Motivation and Context

Module-level setup should be safe when the global API key is unset or blank. Instead of raising during setup, blank API keys now create a disabled no-op global client so module-level calls are ignored consistently.

Changes:

• Strip the module-level API key before creating the global client.
• Treat missing, empty, and whitespace-only global API keys as a disabled no-op client.
• Update the module-level API key/setup documentation to describe the no-op behavior in the return value docs.
• Add parameterized coverage for unset, empty, and whitespace-only API keys.
• Add a Sampo patch changeset for the release note.

💚 How did you test it?

• .venv/bin/python -m pytest posthog/test/test_module.py -q

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

If releasing new changes

• Ran sampo add to generate a changeset file

[greptile-apps]

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
posthog/__init__.py:1066-1072
The blank-key note is floating between the `Returns:` section and `Category:` as an unanchored paragraph, which looks out of place in Google-style docstrings and may render oddly in generated docs. Folding it into the `Returns:` description keeps all return-value semantics in one place.

```suggestion
    Returns:
        The global ``Client`` instance. If ``api_key`` is missing or blank,
        the client is disabled and module-level calls become no-ops.

    Category:
```

_{Reviews (1): Last reviewed commit: "chore: add changeset for blank api key n..." | Re-trigger Greptile}

[github-actions]

posthog-python Compliance Report

Date: 2026-05-28 14:00:01 UTC
Duration: 176120ms

✅ All Tests Passed!

45/45 tests passed

---

Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	516ms
Format Validation.Event Has Uuid	✅	1508ms
Format Validation.Event Has Lib Properties	✅	1506ms
Format Validation.Distinct Id Is String	✅	1508ms
Format Validation.Token Is Present	✅	1506ms
Format Validation.Custom Properties Preserved	✅	1507ms
Format Validation.Event Has Timestamp	✅	1508ms
Retry Behavior.Retries On 503	✅	9519ms
Retry Behavior.Does Not Retry On 400	✅	3505ms
Retry Behavior.Does Not Retry On 401	✅	3508ms
Retry Behavior.Respects Retry After Header	✅	9514ms
Retry Behavior.Implements Backoff	✅	23530ms
Retry Behavior.Retries On 500	✅	7505ms
Retry Behavior.Retries On 502	✅	7512ms
Retry Behavior.Retries On 504	✅	7508ms
Retry Behavior.Max Retries Respected	✅	23532ms
Deduplication.Generates Unique Uuids	✅	1499ms
Deduplication.Preserves Uuid On Retry	✅	7511ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	14525ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	7509ms
Deduplication.No Duplicate Events In Batch	✅	1503ms
Deduplication.Different Events Have Different Uuids	✅	1507ms
Compression.Sends Gzip When Enabled	✅	1507ms
Batch Format.Uses Proper Batch Structure	✅	1507ms
Batch Format.Flush With No Events Sends Nothing	✅	1005ms
Batch Format.Multiple Events Batched Together	✅	1506ms
Error Handling.Does Not Retry On 403	✅	3509ms
Error Handling.Does Not Retry On 413	✅	3508ms
Error Handling.Retries On 408	✅	7514ms

Feature_Flags Tests

✅ 16/16 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	1003ms
Request Payload.Flags Request Uses V2 Query Param	✅	1007ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	1006ms
Request Payload.Flags Request Omits Authorization Header	✅	1007ms
Request Payload.Token In Flags Body Matches Init	✅	1007ms
Request Payload.Groups Round Trip	✅	1006ms
Request Payload.Groups Default To Empty Object	✅	1007ms
Request Payload.Person Properties Distinct Id Auto Populated When Caller Omits It	✅	1007ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	1007ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	1006ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	1007ms
Request Lifecycle.No Flags Request On Init Alone	✅	503ms
Request Lifecycle.No Flags Request On Normal Capture	✅	1507ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	1011ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	1002ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	1509ms