message: JSON. Serializer. Remove extra space char.
diff: @@ -47,7 +47,7 @@ void Serializer::writeList(oatpp::data::stream::ConsistentOutputStream* stream,
  while(curr != nullptr){
  auto value = curr->getData();
  if(value || config->includeNullFields) {
  - (first) ? first = false : stream->write(", ", 2);
  + (first) ? first = false : stream->write(",", 1);
  writeValue(stream, curr->getData(), config);
  }
  curr = curr->getNext();
  @@ -64,10 +64,10 @@ void Serializer::writeFieldsMap(oatpp::data::stream::ConsistentOutputStream* str
  while(curr != nullptr){
  auto value = curr->getValue();
  if(value || config->includeNullFields) {
  - (first) ? first = false : stream->write(", ", 2);
  + (first) ? first = false : stream->write(",", 1);
  auto key = curr->getKey();
  writeString(stream, key->getData(), key->getSize());
  - stream->write(": ", 2);
  + stream->write(":", 1);
  writeValue(stream, curr->getValue(), config);
  }
  curr = curr->getNext();
  @@ -88,9 +88,9 @@ void Serializer::writeObject(oatpp::data::stream::ConsistentOutputStream* stream
  auto value = field->get(object);
  if(value || config->includeNullFields) {
  - (first) ? first = false : stream->write(", ", 2);
  + (first) ? first = false : stream->write(",", 1);
  writeString(stream, field->name);
  - stream->write(": ", 2);
  + stream->write(":", 1);
  writeValue(stream, value, config);
  }
  