Hi Vincent -- thanks for taking the time to post your solution! I, too, have spent a good bit of time trying to piece together a multipart/form-data compliant payload that my Spring apis would accept. I'm not sure why there is no editor panel for the core http-request node, that would allow the user to include an array of files, buffers, and key/value pairs... or why I never offered to contribute that feature... hmmm.
Lately I've been referring to this answer from Nick for a bit simpler JS function example. It does require that your binary data be in a Buffer, but it avoids the user generated boundaries and interspersed CR/NL bits that are hard to find when they are not perfectly placed.
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