Hello,
I've seen your example on how to upload an image and it works for me, but I don't understand if it's possible to put for example other headers (for example alt_text) as specified here:https://developer.wordpress.org/rest-api/reference/media/#create-a-media-item
You're putting the binary data inside the data field, so I don't know how could I add this fields on this param.

Thanks,