APP-5243: Migrate to httpx (goodbye requests 👋 )

[Aryamanz29]

• Removed requirements files
• Updated GitHub workflows for Docker image builds to use uv sync (without dev dependencies)
• Breaking change: Dropped support for Python 3.8 (httpx-retries requires Python ≥ 3.9)

Other v8 Release Tasks:

• Add Python version in headers
• Add Prefetch paginator
• Reduce test build time & coverage report generation
  (explore label-based test runs for async tests)
• Fix SDK Sphinx docs build
• Fix conda packages publish GitHub Action
• Complete final SDK benchmarking
• Create async dev docs (TBD)

✨ Description

Briefly explain the purpose of this PR and what it covers. Mention any related issues or Jira tickets.

Jira link:

• https://atlanhq.atlassian.net/browse/APP-5243
• https://atlanhq.atlassian.net/browse/APP-7641

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🧩 Type of change

Select all that apply:

• 🚀 New feature (non-breaking change that adds functionality)
• 🐛 Bug fix (non-breaking change that fixes an issue) — please include tests! Refer testing-toolkit 🧪
• 🔄 Refactor (code change that neither fixes a bug nor adds a feature)
• 🧹 Maintenance (chores, cleanup, minor improvements)
• 💥 Breaking change (fix or feature that may break existing functionality)
• 📦 Dependency upgrade/downgrade
• 📚 Documentation updates

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✅ How has this been tested? (e.g. screenshots, logs, workflow links)

Describe how the change was tested. Include:

• Steps to reproduce
• Any relevant screenshots, logs, or links to successful workflow runs
• Details on environment/setup if applicable

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📋 Checklist

• My code follows the project’s style guidelines
• I’ve performed a self-review of my code
• I’ve added comments in tricky or complex areas
• I’ve updated the documentation as needed
• There are no new warnings from my changes
• I’ve added tests to cover my changes
• All new and existing tests pass locally

[Copilot]

Pull Request Overview

Migrates the SDK from requests to httpx (using httpx-retries) and drops Python 3.8 support, updating tests, dependencies, and CI workflows accordingly.

• Refactored AtlanClient to use httpx.Client with RetryTransport and new timeout/streaming logic
• Updated unit and integration tests to mock and assert against httpx behavior
• Removed requests from dependencies, bumped requires-python to ≥ 3.9, and adjusted GitHub Actions to no longer test on 3.8

Reviewed Changes

Copilot reviewed 14 out of 16 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tests/unit/test_query_client.py	Adapted mocks to support httpx streaming and reading
tests/unit/test_file_client.py	Updated mocks and assertions for httpx file streaming
tests/unit/test_base_vcr_yaml.py	Replaced requests calls with httpx equivalents
tests/unit/test_base_vcr_json.py	Replaced requests calls with httpx equivalents
tests/integration/test_index_search.py	Swapped requests exceptions and imports for httpx
requirements-dev.txt	Removed legacy dev requirements file
pyproject.toml	Dropped Python 3.8, removed requests, added httpx
pyatlan/client/common.py	Switched retry import from urllib3 to httpx-retries
pyatlan/client/atlan.py	Refactored client setup, API calls, timeout and streams
pyatlan/client/asset.py	Wrapped retry errors in _wait_till_deleted
.github/workflows/pyatlan-test-cron.yaml	Updated Python matrix to ≥ 3.9
.github/workflows/pyatlan-publish.yaml	Changed uv sync to omit dev dependencies
.github/workflows/pyatlan-pr.yaml	Dropped 3.8 from PR and vulnerability-scan inputs
.github/workflows/build_and_upload_conda_packages.yaml	Removed 3.8 from conda build matrix

Comments suppressed due to low confidence (1)

.github/workflows/pyatlan-pr.yaml:40

• [nitpick] Changing the vulnerability-scan inputs to scan the entire workspace may include unintended files. Specify the exact dependency files (e.g., requirements lock files) to limit the scan surface and reduce noise.

            inputs: .

[cursor]

Bug: Incorrect Return Type Annotations in Metadata Cache

The static methods get_attr_id_for_name and get_attribute_def in CustomMetadataCacheCommon have incorrect return type annotations. Both are declared to return a tuple[..., bool] but only return the first element of the tuple, leading to type checking errors and potential runtime issues.