http://forum.bubble.io/t/re-api-connector-post-body-as-a-binary-file/172100/6?u=rowntreerob is response to similar need - a utility to make it easier for endpoints and or api connections to move binary files around among 3rd party services like AWS S3.
Related UI client code based on native html tag for file is here Note: that the server can protect credentials/ auth for 3rd party PAAS. Note: that the stream implementation on server allows it to act as a proxy ( Node.pipes ) sending the file anywhere else.