[KB-6] knowledge_base: complex_variables_and_lookups #17

Roadmap ID: KB-6

type: complex cluster specs per target; lookups for cluster_policy, service_principal, cluster, job, metastore; .databricks/bundle/<target>/variable-overrides.json.

Acceptance criteria

• Each lookup type demonstrated
• Complex variable overridden per target
• README explains precedence (CLI flag > env > overrides file > default)

Edge-case checklist

• AWS / Azure / GCP support matrix (storage URIs, identity, node types, region availability)
• Serverless vs classic both validated, or the unsupported one documented
• No secrets in templates; use secret scopes / workload identity
• Dev schedules paused; no always-on costly resources in tests
• Re-deploy is idempotent; an interrupted deploy is safe to retry
• Teardown only removes resources the example owns

Source: repo gap audit of knowledge_base/ and contrib/ (2026-10-21).