code: @Validate
      public void start() {
          module = new SimpleModule(MonitorExtension.class.getName());
          module.addSerializer(MonitorExtension.class, new JsonSerializer<MonitorExtension>() {
              @Override
              public void serialize(MonitorExtension monitorExtension, JsonGenerator jsonGenerator,
                                    SerializerProvider serializerProvider) throws IOException {
                  jsonGenerator.writeStartObject();
                  jsonGenerator.writeStringField("label", monitorExtension.label());
                  jsonGenerator.writeStringField("url", monitorExtension.url());
                  jsonGenerator.writeStringField("category", monitorExtension.category());
                  jsonGenerator.writeEndObject();
              }
          });
          repository.register(module);
      }
docs: When the monitor starts, we initializes and registers a JSON module handling the serialization of
  the monitor extension.