Create post replies from the API#2649

I would like to be able to create replies from the API.

I think that it could be fairly easy to add this feature without having to create a new entry point. Simply add a field “parent_url” to an existing JSON object of post publish request could do it.

Also, this feature could be an intermediary milestone toward the thread creation feature request or a building block

With the feature in place, someone could create a thread using this low-level function