feat!: Make HTTP client pluggable with abstract base classes

[vdusek]

Summary

• Introduce HttpClient and HttpClientAsync ABCs that users can extend to provide custom HTTP client implementations via ApifyClient(http_client=...) and ApifyClientAsync(http_client=...)
• Factor impit-specific logic into ImpitHttpClient/ImpitHttpClientAsync, keeping _base.py free of any impit dependency
• Add HttpResponse protocol with full streaming support (iter_bytes, aiter_bytes, read, aread, close, aclose)
• Export all public types (HttpClient, HttpClientAsync, HttpResponse, ImpitHttpClient, ImpitHttpClientAsync) from apify_client

Issue

• Closes: Allow to pass own http_client to ApifyClient and ApifyClientAsync #416

Test plan

• CI passes

[codecov]

Codecov Report

❌ Patch coverage is 91.26214% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.59%. Comparing base (230bb64) to head (17f504b).
⚠️ Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
src/apify_client/_apify_client.py	90.69%	4 Missing ⚠️
src/apify_client/_utils.py	62.50%	3 Missing ⚠️
src/apify_client/_http_clients/_base.py	93.93%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #641      +/-   ##
==========================================
- Coverage   96.62%   96.59%   -0.04%     
==========================================
  Files          45       46       +1     
  Lines        4271     4433     +162     
==========================================
+ Hits         4127     4282     +155     
- Misses        144      151       +7     

Flag	Coverage Δ
integration	94.76% <82.52%> (+0.08%)	⬆️
unit	76.51% <91.26%> (+0.91%)	⬆️

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[Copilot]

Pull request overview

This PR makes the Apify Python client’s HTTP transport layer pluggable by introducing public abstract base classes (HttpClient, HttpClientAsync) and an HttpResponse protocol, while moving the default impit-backed implementation into ImpitHttpClient / ImpitHttpClientAsync. It also wires the new http_client=... injection into ApifyClient / ApifyClientAsync and updates type hints and tests accordingly.

Changes:

• Add HttpResponse protocol plus HttpClient / HttpClientAsync ABCs, and move impit implementation into ImpitHttpClient / ImpitHttpClientAsync.
• Allow passing a custom http_client into ApifyClient and ApifyClientAsync, and export the new public HTTP types from apify_client.
• Update resource-client type hints and expand unit tests to cover custom client behavior and streaming.

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/unit/test_pluggable_http_client.py	New unit tests validating ABC/protocol conformance and custom http_client injection behavior (sync + async).
tests/unit/test_http_clients.py	Updates tests to target ImpitHttpClient* for retry logic and adds concrete ABC implementations for base-helper testing.
tests/unit/test_client_timeouts.py	Switches tests to use ImpitHttpClient* (since HttpClient* are now abstract).
tests/unit/test_client_headers.py	Switches tests to use ImpitHttpClient* for header behavior.
tests/unit/test_client_errors.py	Switches tests to use ImpitHttpClient* and keeps streamed-error coverage.
src/apify_client/errors.py	Generalizes error types to accept HttpResponse instead of impit.Response.
src/apify_client/_utils.py	Generalizes response-parsing helpers to HttpResponse and updates docstrings accordingly.
src/apify_client/_resource_clients/task.py	Docstring formatting adjustment (no functional behavior change).
src/apify_client/_resource_clients/log.py	Generalizes streaming return types to HttpResponse.
src/apify_client/_resource_clients/key_value_store.py	Generalizes record parsing function signature to HttpResponse.
src/apify_client/_resource_clients/dataset.py	Generalizes streaming item types to HttpResponse.
src/apify_client/_http_clients/_impit.py	Introduces ImpitHttpClient* and factors retryability logic; keeps default impit implementation.
src/apify_client/_http_clients/_base.py	Adds HttpResponse protocol and HttpClient* ABCs; keeps shared request-prep helpers in _HttpClientBase.
src/apify_client/_http_clients/init.py	Re-exports HttpClient*, HttpResponse, and default ImpitHttpClient*.
src/apify_client/_apify_client.py	Adds http_client parameter, defaults to ImpitHttpClient*, and exposes http_client property.
src/apify_client/init.py	Exports the new HTTP types from the public apify_client package.

Comments suppressed due to low confidence (2)

src/apify_client/_http_clients/_impit.py:16

• _impit.py imports HttpClient/HttpClientAsync from the package (apify_client._http_clients), but that package’s __init__ also imports _impit, creating an avoidable circular import that can become fragile depending on import order. Import these symbols directly from ._base (and HttpResponse from ._base under TYPE_CHECKING) to break the cycle.
  src/apify_client/_http_clients/_impit.py:44
• There are now two sources of truth for retryability (apify_client._utils.is_retryable_error and _http_clients._impit._is_retryable_error) with identical logic. This duplication risks the rules drifting over time; consider reusing the existing helper from _utils here, or otherwise removing/consolidating one of them so tests and the impit client validate the same implementation.

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[Pijukatel]

Nice. The only drawback I see is the initialization with conflicting arguments. Maybe we can figure out something better.