public static Function<? super HttpService, ObservationService>
    newDecorator(ObservationRegistry observationRegistry,
                 ObservationConvention<ServiceObservationContext> observationConvention) {
        requireNonNull(observationRegistry, "observationRegistry");
        requireNonNull(observationConvention, "observationConvention");
        return service -> new ObservationService(
                service, observationRegistry, observationConvention);
    }
Creates a new micrometer observation integrated {@link HttpService} decorator using the
specified {@link ObservationRegistry} and {@link ObservationConvention}.
core/src/main/java/com/linecorp/armeria/server/observation/ObservationService.java