Denials were invisible in the audit trail and evaluator explainability
(policy_id, reason) was discarded before reaching logs. Emit a structured
authz decision line on every evaluation in evaluateMultiInTx — allow,
deny, no_match, and assumption errors — using the existing authorizer
logger with opaque IDs only.
Add decision_log.go with DecisionRecord and logDecision. Surface
PolicyID and Reason on EvaluationResult for logging. Audit log
behavior is unchanged (allow-only). Document the convention in
authorization.md.
Signed-off-by: Ludovic Vielle <ludovic@probo.com>
71e8d662bc