public GrpcJsonMarshallerBuilder jsonMarshallerCustomizer(
            Consumer<? super MessageMarshaller.Builder> jsonMarshallerCustomizer) {
        requireNonNull(jsonMarshallerCustomizer, "jsonMarshallerCustomizer");
        if (this.jsonMarshallerCustomizer == null) {
            @SuppressWarnings("unchecked")
            final Consumer<Builder> cast = (Consumer<Builder>) jsonMarshallerCustomizer;
            this.jsonMarshallerCustomizer = cast;
        } else {
            this.jsonMarshallerCustomizer = this.jsonMarshallerCustomizer.andThen(jsonMarshallerCustomizer);
        }
        return this;
    }
Sets a {@link Consumer} that can customize the JSON marshaller for {@link Message} used when handling
JSON payloads in the service. This is commonly used to switch from the default of using lowerCamelCase
for field names to using the field name from the proto definition, by setting
{@link MessageMarshaller.Builder#preservingProtoFieldNames(boolean)}.
grpc/src/main/java/com/linecorp/armeria/common/grpc/GrpcJsonMarshallerBuilder.java