Two new test files driving the next commit's admin UI work.
tests/test_admin_bigquery_test_connection.py — POST
/api/admin/bigquery/test-connection (admin-only health probe). 6 cases:
- success → 200 with ok=true + resolved billing_project / data_project
/ elapsed_ms
- not_configured → 400 with the typed BqAccessError detail surface
- cross_project_forbidden (USER_PROJECT_DENIED simulation) → 502
- 10s timeout → 504 with kind="timeout" (best-effort cancel_job)
- non-admin caller → 403
- unauthenticated → 401
The endpoint matters for the operator side of the reporter's loop —
admin saves data_source.bigquery in /admin/server-config, clicks
"Test connection", gets typed structured feedback BEFORE any analyst
hits a query failure.
tests/test_admin_server_config_placeholder.py — `billing_project`
field-spec must carry `placeholder_from: ["data_source", "bigquery",
"project"]` so the JS template can resolve and inject
"(defaults to <project>)" greyed under the input when the operator
hasn't set billing_project explicitly. This makes the existing
"billing falls back to data" rule (connectors/bigquery/access.py:
339-340) visible in the UI.
7 RED on the current branch (endpoint and placeholder_from key both
absent). GREEN landing in the next commit.
