Migrate SDK HTTP stack to httpx2

[goncalossilva]

Summary

• replace the direct httpx runtime dependency with httpx2>=2.0.0,<3
• migrate sync, async, authentication, response, timeout, and public injected-client types to httpx2
• route the existing RESPX-backed tests through the maintained pytest-httpx2 plugin
• update the lockfile, README, API docs, and changelog

Compatibility

This is a breaking change for callers that pass an httpx.Client or httpx.AsyncClient, or catch httpx exceptions: httpx and httpx2 expose distinct classes, so those objects and exception handlers must move to httpx2 too.

HTTPX2 also changes the default User-Agent to python-httpx2/<version>, uses the httpx2 and httpcore2.* logger names, and verifies TLS through the operating system trust store instead of Certifi. Callers that need a specific trust policy can continue to supply a configured httpx2 client.

httpx remains in the development lock graph only as a transitive dependency of RESPX; it is no longer an SDK runtime dependency.

Verification

• uv sync --group dev
• uv run tox — 88 tests passed on Python 3.10, 3.11, 3.12, 3.13, and 3.14
• changed-file pre-commit suite — passed (Ruff lint/format, mypy, and lock check included)
• uv run mypy todoist_api_python — passed
• uv lock --check — passed
• uv build — built the sdist and wheel

uv run ruff check . and uv run mypy . still report the same 7 and 15 pre-existing findings, respectively, as current main; changed-file checks pass.

[doistbot]

This PR updates Migrate SDK HTTP stack to httpx2. No issues were flagged in the reviewed diff.

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[goncalossilva]

@doistbot /review

[doistbot]

This PR updates Migrate SDK HTTP stack to httpx2. No issues were flagged in the reviewed diff.

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