Attach severity-aware asset checks to a Dagster asset and control whether failures block downstream materialization

Steps

1. Define a check with @asset_check(asset=my_asset) returning an AssetCheckResult(passed=...), or attach inline check_specs=[AssetCheckSpec(...)] on the @asset definition itself.
2. Set the check's severity — ERROR is the default; use AssetCheckSeverity.WARN explicitly when a failure should be visible but shouldn't stop anything downstream.
3. To actually block downstream materialization on failure, combine blocking=True on the check with ERROR severity — severity alone does not stop execution.
4. Leave blocking unset (or use WARN severity) for purely observational checks, e.g. data quality signals surfaced in the UI without gating the pipeline.
5. Review pass/fail/warn trends in the Dagster UI's asset check history rather than only reacting to the latest run.