Idea: allow profiles to be requested on the new_post endpoint

[quentez]

Often, when creating a new post mentioning other users, an app will end up retrieving the profiles for these. An option could be to allow the same profiles parameter that's available on other endpoints to instruct the server to return the specified user profiles along with the newly created post.

This could also be extended to refs (or 0.4 links) to get the server to return the related posts.