private Mono<ServerResponse> listNotificationPreferences(ServerRequest request) {
        var username = request.pathVariable("username");
        return listReasonTypeNotifierMatrix(username)
            .flatMap(matrix -> ServerResponse.ok().bodyValue(matrix));
    }
@Test
    void listNotificationPreferences() {
        when(client.list(eq(ReasonType.class), eq(null), any())).thenReturn(Flux.empty());
        when(client.list(eq(NotifierDescriptor.class), eq(null), any())).thenReturn(Flux.empty());
        when(userNotificationPreferenceService.getByUser(any())).thenReturn(Mono.empty());
        webTestClient.post()
            .uri("/userspaces/{username}/notification-preferences", "guqing")
            .exchange()
            .expectStatus()
            .isOk();
    }