func NewPolicyRuleEvaluator(policy *audit.Policy) auditinternal.PolicyRuleEvaluator {
	for i, rule := range policy.Rules {
		policy.Rules[i].OmitStages = unionStages(policy.OmitStages, rule.OmitStages)
	}
	return &policyRuleEvaluator{*policy}
}

func unionStages(stageLists ...[]audit.Stage) []audit.Stage {
	m := make(map[audit.Stage]bool)
	for _, sl := range stageLists {
		for _, s := range sl {
			m[s] = true
		}
	}