I'm trying to post an image to a product, but on post I dont know where exactly to put it. Should I put on custom_attributes as when I get it on GET ? Didn't have success, even using image, small_image and thumbnail and the same link image as one that I added manually. Or should I use other way like Media Gallery Entries? If so could I get an example? because on documentation they only tell me things like "string" and don't know which are the possibilities.