feat(python): add Python OpenFeature provider

[nicklasl]

Summary

Add Python OpenFeature provider for Confidence feature flags with WASM-based local resolution.

Components Implemented

• WasmResolver (wasm_resolver.py): Low-level WASM runtime using wasmtime for flag resolution
• LocalResolver (local_resolver.py): Crash recovery wrapper with automatic WASM reload and state restoration
• StateFetcher (state_fetcher.py): CDN state fetching with ETag caching and 304 handling
• FlagLogger (flag_logger.py): Async gRPC flag logging with ThreadPoolExecutor
• MaterializationStore (materialization.py): Protocol and implementations for sticky assignments and segment inclusion
• ConfidenceProvider (provider.py): Main OpenFeature provider implementation

Features

• Local WASM-based flag resolution for low latency
• Background state polling from CDN (configurable interval)
• Async flag/assignment logging via gRPC
• Thread-safe resolver access with Lock
• Materialization store support (sticky assignments and segment inclusion)
• Remote materialization store for server-side storage
• Crash recovery with automatic WASM reload and state restoration
• Support for nested flag paths (e.g., my-flag.nested.value)
• Logging via Python standard logging module

Build

• Docker stages: openfeature-provider-python.{test,test_e2e,lint,build,artifact}
• WASM built from source (not committed), copied from wasm-rust-guest.artifact in Docker

Usage

from openfeature import api
from confidence_openfeature import ConfidenceProvider

provider = ConfidenceProvider(client_secret="your-client-secret")
api.set_provider(provider)

client = api.get_client()
result = client.get_boolean_value("my-flag.enabled", default_value=False)

Logging

Configure logging to see provider activity:

import logging
logging.getLogger("confidence_openfeature").setLevel(logging.DEBUG)

Test plan

• 65 unit tests passing (make test)
• 6 E2E tests passing (make test-e2e)
• Lint clean (make lint - black, flake8, mypy)
• Docker build for all stages

🤖 Generated with Claude Code

[nicklasl]

There are 3 fallbacks due to Python's evolving resource loading APIs:

1. importlib.resources.files() (Python 3.9+)
   - The modern, recommended approach
   - Works with installed packages and namespace packages
   - Returns a traversable object
2. pkg_resources (setuptools legacy)
   - Old approach, being deprecated (see the warning in tests)
   - Still needed for older Python/setuptools combinations
   - Works when importlib.resources doesn't find the file
3. Development fallback (Path-based)
   - For local development with pip install -e .
   - When WASM is in resources/wasm/ but not yet packaged into the wheel
   - Useful during development before running make build

This complexity exists because:

• Python's resource loading has changed significantly between versions
• Editable installs (pip install -e .) behave differently than regular installs
• The WASM file location differs between development and packaged states

We could simplify this by requiring Python 3.11+ (which has stable importlib.resources), but the current code supports Python 3.9+.