feat: switch client generation to openapi-python-client

[mekilis]

Summary

Speakeasy's free tier allows one generated SDK per workspace and convoy.js holds that slot, so Python client generation moves to the OSS openapi-python-client (pinned 0.29.0).

• sdk_generation.yaml rewritten for openapi-python-client. Same filename and dispatch inputs (force, feature_branch), so the frain-dev/convoy dispatcher works unchanged. Opens a PR only when the regenerated client differs.
• Speakeasy pipeline kept dormant, not deleted: old workflow renamed to speakeasy_generation.yaml (manual-only), .speakeasy/ and .genignore kept current so switching providers back is a trigger change, not a rebuild.
• scripts/generate.sh fetches the spec, generates with --fail-on-warning, and rsyncs into src/convoy/ excluding hand-written verify (src/convoy/utils/) and py.typed — same protection contract .genignore gave Speakeasy.
• Hand-owned pyproject.toml (convoy-python 1.0.0a1, deps httpx + attrs).
• MIGRATION.md / README updated.

Test plan

• scripts/generate.sh run locally against the live spec: all 67 operations generated, src/convoy/utils/ untouched
• Wheel build carries verify + generated client + py.typed (548 files)
• Pre-generation tree (this PR's state) installs with pip install -e .; from convoy.utils.webhook import Webhook resolves from the installed distribution
• pytest test/test_webhook.py test/test_shared_vectors.py: 29 passed (pre- and post-generation)

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Note

Medium Risk
Touches release/CI generation and uses rsync --delete on src/convoy/; mis-excludes could affect hand-written webhook verify, though excludes and docs explicitly protect utils/.

Overview
Python HTTP client generation moves from Speakeasy to pinned openapi-python-client, while keeping the same sdk_generation.yaml entrypoint and dispatch inputs so upstream dispatchers stay compatible.

The active sdk_generation workflow now installs openapi-python-client/ruff, runs scripts/generate.sh, and only opens or updates a PR when the regenerated tree differs. Speakeasy is not removed: its workflow is renamed to speakeasy_generation.yaml (manual-only), with .genignore and .speakeasy/ kept current for an easy provider switch-back.

Hand-owned packaging and sync rules are added: pyproject.toml (convoy-python 1.0.0a1), .openapi-python-client.yml (package_name_override: convoy), and generate.sh (fetch spec, generate with --fail-on-warning, rsync --delete into src/convoy/ while excluding utils/ and py.typed). .genignore documents the same protected paths for a dormant Speakeasy path.

Test CI always pip install -e . and runs verify tests from the installed distribution—pre-generation PYTHONPATH fallbacks are removed. MIGRATION.md / README describe openapi-python-client as the active generator.

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