According to the API documentation all I need to supply is a value for "minorEdit" and "file" with a filepath, but even if I provide no body at all I get the same error "...BadRequestException: At least one attachment file must be included". I wondered if maybe it needs the ACTUAL file not just the path so I tried including content type and base64 encoded text of my image. Also wondered why the documentation says "relative file path"... relative to what? But I'm thinking it's failing before that point altogether: I don't think I'm constructing the body content correctly: does this LOOK correct?
--IMabOUnDArY
Content-Disposition: form-data; name="minorEdit"
"true"
--IMabOUnDArY
Content-Disposition: form-data; name="file"
"C:\Users\me\ParsedHTML\Input\Files\DiagramSMK-191453.jpg"
--IMabOUnDArY--
Or I found this post Solved: Uploading attachment into Confluence (atlassian.com) which seems to include the actual file content in the post (although it doesn't mention that on the API documentation, that seems more logical?) but that doesn't work either? Should I try different characters for carriage return new line perhaps?