test(session): exercise the deprecated SessionMiddleware over HTTP

[allen0099]

Summary

Closes #188

Part of #123.

tests/session/test_middleware.py now tests the deprecated SessionMiddleware the way an app uses it:

• it is installed with app.add_middleware;
• requests go through TestClient;
• results are read through get_optional_session and the response headers.

The tests no longer call _extract_token, _get_client_ip or dispatch on a hand-built instance.

Several old "dispatch" tests constructed SessionMiddleware(app, ...) without installing it. Their requests never reached the middleware, and they only asserted status_code == 200.

The DeprecationWarning is now expected explicitly:

• The _client() helper wraps the warm-up request in pytest.warns. Starlette builds the middleware stack on that first request.
• A dedicated test checks that the message names FastAPICacheXSessionMiddleware.
• Six tests in test_get_session_manager.py and test_dependencies.py use the deprecated middleware only as scaffolding. They get a targeted filterwarnings("ignore:SessionMiddleware is deprecated:DeprecationWarning"). Their fixtures are untouched, to keep the conflict with Tests: move shared session fixtures to tests/session/conftest.py #187 small.

What replaces what

Old test (private API or not installed)	New test
test_middleware_initialization (middleware.config is config)	test_an_explicit_config_overrides_the_managers: the override's header is read, the default header is not
test_middleware_initialization_uses_manager_config	test_config_defaults_to_the_managers: a custom header on the manager's config is honoured
(none)	test_the_manager_defaults_to_the_proxy: session_manager=None falls back to SessionManagerProxy
test_extract_token_from_header, test_dispatch_sets_session_in_request_state, test_dispatch_direct_call	test_a_header_token_loads_the_session: session ID and user, and no token header in the response
test_extract_token_from_bearer	test_a_bearer_token_loads_the_session
test_extract_token_none, test_extract_token_from_bearer_with_malformed_header, test_dispatch_with_invalid_session, test_dispatch_with_no_session, test_dispatch_with_session_error	test_a_missing_or_invalid_token_loads_no_session: no token, invalid header token, empty and invalid Bearer
test_dispatch_with_expired_session	test_an_expired_session_is_not_loaded: now asserts the session is absent
test_dispatch_with_session_and_ip_binding	test_ip_binding_checks_the_peer_address: match loads, mismatch does not
test_get_client_ip_* via middleware._get_client_ip	same cases via the public get_client_ip, plus test_ip_binding_uses_the_forwarded_address_behind_a_trusted_proxy end to end
test_dispatch_with_user_agent_binding	test_user_agent_binding_checks_the_request_user_agent: match and mismatch
(none in this file)	test_a_rotated_session_id_is_sent_back_as_a_new_token: rotate_session_id gives a new header token, and the old one no longer resolves
test_dispatch_sets_renewed_token_header_on_sliding_expiration	test_sliding_expiration_sends_the_renewed_token (same assertions, via the helper)

The _extract_header_token fallback-chain tests at the bottom of the file are unchanged. Their _connection helper gained an optional peer.

Tests

• uv run pytest tests/session/test_middleware.py -W error::DeprecationWarning: 40 passed, on Python 3.10 and 3.14. uv run pytest tests/session -W error::DeprecationWarning: 248 passed. Before this PR, 28 tests failed under that flag.
• Coverage of fastapi_cachex/session/middleware.py from test_middleware.py alone went from 53% to 54%. The SessionMiddleware class is now fully covered by this file; before, the no-token branch (231->247) and the regenerated-ID branch (257) were missed.
• Full suite without live servers: before, 841 passed and 190 skipped; after, 845 passed and 190 skipped. middleware.py stays at 99% (the one partial is 473->exit, in the other middleware). Total stays at 94%. The run now emits 6 warnings instead of 34; the remaining ones are the JWT short-key warnings, which are for Tests: tighten the pytest configuration #189.
• Mutation checks, each run against the full suite:
  • Dropping the regenerated-ID branch in dispatch fails test_a_rotated_session_id_is_sent_back_as_a_new_token and the two existing test_deprecated_middleware_sends_regenerated_token cases.
  • Resolving the client IP from the peer, ignoring trusted_proxies, fails only test_ip_binding_uses_the_forwarded_address_behind_a_trusted_proxy[203.0.113.7-True].
  • Defaulting config to a fresh SessionConfig instead of the manager's fails only test_config_defaults_to_the_managers.
• ruff check and ruff format are clean; pre-commit passed on commit.

CHANGELOG

None: test-only.