Adds an attachment to an existing draft invoice. The attachment will be added last in the list of attachments on the invoice. Attached files will appear as additional pages in the final invoice

Supported file types: jpeg, png and pdf

Show example of multipart MIME as we do for uploads

NOTE: The invoice must be in draft status. Maximum file size is 4 MB and all files can't exceed 10 MB. Dimensions must be less than height of 7016 and width of 4960 in pixels

Scope: invoices:write