Here is some more info. Recent implementation of our API was done in nostril.ninja and here is their code https://github.com/hzrd149/nostrudel/blob/master/src/helpers/nostr-build.ts Also, here:

GitHub

Use nostr build apiv2 by fishcakeday · Pull Request #440 · irislib/iris-messenger

This should implement usage of new nostr.build api and use nip-98 for uploads.

And lastly: https://github.com/coracle-social/coracle/blob/master/src/engine/media/commands.ts Let me know if this helps or if you need more info. Thanks. 🐶🐾🫡