fix: propagate client metadata to the gateway

[nicholaspun-wandb]

Adds the SDK version and optionally the integration source as headers so that we can track this at the gateway. This will allow us to better understand SDK rollout and also which integrations are receiving usage.

[nicholaspun-wandb]

e2e tests:

uv run --no-sync pytest tests/integration/ -p wandb.sandbox -n auto

======================================================= short test summary info ========================================================
FAILED tests/integration/cwsandbox/test_discovery.py::TestListRunners::test_capacity_filter - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
FAILED tests/integration/cwsandbox/test_discovery.py::TestGetProfile::test_get_nonexistent_profile - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
FAILED tests/integration/cwsandbox/test_discovery.py::TestListRunners::test_filter_nonexistent_profile - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
FAILED tests/integration/cwsandbox/test_discovery.py::TestGetRunner::test_get_nonexistent_runner - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_discovery.py::TestListRunners::test_include_resources_false_default - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_discovery.py::TestListRunners::test_filter_by_architecture - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_discovery.py::TestListProfiles::test_filter_by_service_exposure_mode - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_discovery.py::TestGetProfile::test_get_existing_profile - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_discovery.py::TestListProfiles::test_profile_fields_populated - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_discovery.py::TestGetRunner::test_get_existing_runner - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_discovery.py::TestListProfiles::test_filter_by_egress_mode - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_discovery.py::TestListRunners::test_runner_fields_populated - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_discovery.py::TestListRunners::test_filter_by_profile_name - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_discovery.py::TestCrossReference::test_profile_runner_ids_exist - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_discovery.py::TestGetRunner::test_get_runner_always_has_full_details - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_discovery.py::TestListProfiles::test_filter_by_runner_id - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_discovery.py::TestGetProfile::test_get_profile_without_runner_id - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_discovery.py::TestListProfiles::test_filter_by_architecture - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_discovery.py::TestListProfiles::test_returns_profiles - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_discovery.py::TestListRunners::test_filter_by_runner_group_id - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_discovery.py::TestListRunners::test_include_resources_true - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_discovery.py::TestListRunners::test_returns_runners - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_discovery.py::TestCrossReference::test_runner_profiles_match_list_profiles - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_sandbox.py::test_sandbox_pinned_to_runner - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_sandbox.py::test_sandbox_pinned_to_profile - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
ERROR tests/integration/cwsandbox/test_sandbox.py::test_sandbox_pinned_to_profile_and_runner - cwsandbox.exceptions.CWSandboxAuthenticationError: Permission denied: W&B auth is not allowed for this sandbox operation
========================================= 4 failed, 91 passed, 1 skipped, 22 errors in 49.73s ==========================================

CWSANDBOX_BASE_URL=http://localhost:8080 \
CWSANDBOX_API_KEY=key1 \
uv run pytest \
tests/integration/cwsandbox/test_discovery.py \
tests/integration/cwsandbox/test_sandbox.py::test_sandbox_pinned_to_profile_and_runner \
tests/integration/cwsandbox/test_sandbox.py::test_sandbox_pinned_to_profile \
tests/integration/cwsandbox/test_sandbox.py::test_sandbox_pinned_to_runner \
tests/integration/cwsandbox/test_file_system_snapshot.py \
-n 6
========================================================= test session starts ==========================================================
platform darwin -- Python 3.11.10, pytest-9.0.2, pluggy-1.6.0
rootdir: /Users/nicholaspun/Documents/cwsandbox-client
configfile: pyproject.toml
plugins: anyio-4.12.1, xdist-3.8.0, asyncio-1.3.0, dotenv-0.5.2, cov-7.0.0
asyncio: mode=Mode.AUTO, debug=False, asyncio_default_fixture_loop_scope=None, asyncio_default_test_loop_scope=function
6 workers [29 items]    
.............................                                                                                                    [100%]
==================================================== 29 passed in 75.50s (0:01:15) =====================================================

[NavarrePratt]

Is this going to be used by external callers like the wandb library? If so we should import it within __init__.py, like we do for set_auth_mode.