Support overriding API key at request-time

[keyurva]

• Adds ause_api_key context manager to override the API key for specific request scopes.
• Enables using different keys without re-instantiating the client, useful for multi-tenant applications (like hosted mcp servers).
• Ensures the overridden key is correctly propagated even for methods that rely on worker threads (e.g. node.fetch_place_ancestors).

from datacommons_client import use_api_key

# Standard usage (uses client default key)
client.observation.fetch(...)

# Usage with override
with use_api_key("new-scoped-key"):
    client.observation.fetch(...)
    # Works for threaded methods too
    client.node.fetch_place_ancestors(...)

[gemini-code-assist]

Summary of Changes

Hello @keyurva, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the datacommons_client by introducing a flexible way to manage API keys at request-time. A new use_api_key context manager allows users to temporarily override the default API key for specific blocks of code, which is particularly useful for multi-tenant applications or scenarios requiring dynamic key switching. The implementation ensures that this contextual API key is correctly applied across all client operations, including those that leverage multi-threading, by integrating Python's contextvars module.

Highlights

• New Context Manager: Introduced a use_api_key context manager that allows overriding the API key for specific request scopes without re-instantiating the client.
• API Key Propagation: Implemented mechanisms to ensure the overridden API key is correctly propagated to all HTTP requests, including those made within worker threads (e.g., node.fetch_place_ancestors).
• Context Variable Integration: Utilized Python's contextvars module to manage and propagate the API key across different execution contexts, including those involving ThreadPoolExecutor.
• Comprehensive Testing: Added new unit and integration tests to validate the functionality of the use_api_key context manager for both single-threaded and multi-threaded API calls, covering basic usage, nesting, and edge cases.

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[gemini-code-assist]

Code Review

This pull request introduces a use_api_key context manager to allow overriding the API key for specific requests. This is a valuable feature for multi-tenant applications. The implementation correctly uses contextvars to manage the key, ensuring it's propagated to worker threads for asynchronous operations. The changes are well-tested, with new unit tests for the context manager and integration tests for both synchronous and threaded client methods.

My review includes a couple of suggestions to improve code style and consistency:

• Moving a local import to the top of the file to adhere to PEP 8.
• Aligning the testing style in a new test file with the existing pytest conventions for better project consistency.

Overall, this is a great addition to the client library.

[clincoln8]

Very cool, thanks Keyur!

Are you planning on publishing to TestPyPi first?
Will we update the python v2 docs to include info about this option?

[keyurva]

Thanks for the review!

Are you planning on publishing to TestPyPi first?

Yes. Will follow the release process in https://github.com/datacommonsorg/api-python/blob/master/docs/release.md which includes publishing to TestPyPi

Will we update the python v2 docs to include info about this option?

Hmm - not sure if users of the library will be using this option so not sure about updating docs either.

WDYT? Also, @kmoscoe - thoughts?