public Optional<AthenzService> athenzService(Environment environment, RegionName region) {
        return zones().stream()
                      .filter(zone -> zone.concerns(environment, Optional.of(region)))
                      .findFirst()
                      .flatMap(DeploymentSpec.DeclaredZone::athenzService)
                      .or(() -> athenzService);
    }
Returns the athenz service for environment/region if configured, defaulting to that of the instance
config-model-api/src/main/java/com/yahoo/config/application/api/DeploymentInstanceSpec.java