Attach a document to an existing book entry that doesn't have any document yet. The result will contain the generated document's id.

Use the multipart/form-data content type and add two arguments. The first one must be named file and contain the file's bytes, and the other one must be named body and contain the json-formatted information.

Supported document types :

• Pdf
• Xml
• CODA
• SODA
• Images (.jpg, .jpeg, .png)

The request will fail if a document is already attached to the book entry. In that case, use the endpoint 'book-entries.documents.annexes.new'.