[alexanto]

in this PR, I start doing what I set out to really do in the first place

made the generic transport public in the sync client, so users can now bring their own trasport implementation and use a different http library other than requests or they can inject a session only depending their needs. haven't removed HttpOptions yet, but clearly doesn't sit well with this redesign, coming shortly.

[Copilot]

🟡 Changes recommended

Valid falsey custom transports are silently replaced with the default, causing unintended real HTTP requests, while custom transport users also lose control over the SDK retry budget.

2 open issues

• Use the default transport only when the supplied transport is None · New
• Preserve retry configuration when using a custom transport · New

What changed in this PR

This PR exposes the synchronous client's HTTP transport API, allowing callers to supply a configured requests.Session or use another HTTP library.

Changes:

• Publishes transport types and adds validated transport= injection.
• Adds session reuse, custom transport headers, and case-insensitive response-header lookup.
• Adds documentation, runnable examples, and transport integration tests.

File	Description
UnleashClient/​transport.py	Publishes transport interfaces and configurable requests transport.
UnleashClient/​clients/​unleash_client.py	Validates and forwards custom transports.
UnleashClient/​_unleash_api_client.py	Uses public transport types and case-insensitive ETag lookup.
UnleashClient/​_transport.py	Removes the former private transport module.
UnleashClient/​_retry.py	Imports public transport types.
UnleashClient/​_async_unleash_api_client.py	Updates transport imports.
UnleashClient/​_aiohttp_transport.py	Updates request and response imports.
UnleashClient/​__init__.py	Exports the public sync transport API.
tests/​unit_tests/​test_unleash_api_client.py	Tests case-insensitive response headers.
tests/​unit_tests/​test_transport.py	Tests sessions, headers, timeouts, and retry warnings.
tests/​unit_tests/​test_retry.py	Updates transport imports.
tests/​unit_tests/​test_async_unleash_api_client.py	Updates transport imports.
tests/​unit_tests/​test_aiohttp_transport.py	Updates transport imports.
tests/​unit_tests/​clients/​test_unleash_client_transport.py	Tests transport injection, validation, and examples.
requirements.txt	Adds httpx for testing.
README.md	Documents custom transports and ownership requirements.
pyproject.toml	Excludes examples from package discovery.
examples/​httpx_transport.py	Demonstrates an httpx-backed transport.
examples/​fake_transport.py	Demonstrates server-free feature testing.
CHANGELOG.md	Announces public sync transport support.

_{Review effort: Balanced}