I had been barking up the wrong tree, trying to address `photo/edit` in order to create a photo post in WithKnown. Going through my old notes, I figured out how to do it through `micropub/endpoint` instead, which makes a whole lot more sense. Probably I should have started there.
Anyway, I know have the bare bones of being able to post automatically to WithKnown from the RSS feed of my Instagram account. Now I "just" need to build out all the rest; read the RSS feed, extract the relevant bits of data, construct the API request and bung it off.
Which will probably take forever, but hey.