With the body you
have sent, this is the following message on the call
filecontents is invalid in module Document.
Request is the same as you wrote on your comment.
What i have done so far is that i can create a Document with this body:
After this call am getting the error 400 : Notes module with id db20f96f-171d-4511-4e6a-5ef439898823 is not found. But document still gets created. And it’s the only way to attach a file and working to see that in CRM by adding doc_url, otherwise document is broken.