Lab: Contracts + Exposure + Unit Test (Green dbt build)

# Lab: Contract + Exposure + Unit Test on stg_orders Models (Graded) ## Brief Harden an existing dbt project (starter attached, built on the W4 `stg_orders` shape) with the three enterprise gates. Finish with a green `dbt build`. ## Tasks 1. **Contract:** enforce `mart_daily_revenue` (`day: date not_null`, `revenue_cents: numeric not_null`). Show the build failing first by feeding a bad row, then fix and rebuild green. 2. **Exposure:** declare one `dashboard` exposure for a revenue dashboard reading the mart. Paste `dbt ls --select +exposure: ` output proving lineage resolves. 3. **Unit test:** write a `unit_tests` YAML block for the revenue aggregation (given 3 input rows incl. one refund, expect exact output). `dbt test --select test_type:unit` must pass. ## Acceptance (deterministic checks before review) - `dbt build` exits 0 with contract enforced (paste log tail). - Exposure resolves in `dbt ls` output (paste output). - Unit test passes (paste `dbt test` summary). - One intentional contract-break demonstrated (bad row rejected, paste error). ## Starter Legacy dbt project skeleton + seed CSV + TODO-marked YAML files attached.