POST https://api.ebay.com/post-order/v2/return/5********1/file/upload { "fileName" : "5********1_s***********l.jpeg", "data" : "SGVyZSBpcyB5b3VyIHJld...YWNraW5nIG51bWJlciBpcyAxMjM0NTY3ODk4NzY1", "filePurpose" : "LABEL_RELATED" }