> curl -X POST --data-binary @- --header "Content-Type: multipart/form-data; boundary=XXXsubpartXXX" http://localhost:8529/_api/batch
--XXXsubpartXXX
Content-Type: application/x-arango-batchpart

POST /_api/document?collection=nonexisting

{"a":1,"b":2,"c":3}
--XXXsubpartXXX
Content-Type: application/x-arango-batchpart

POST /_api/document?collection=xyz

{"a":1,"b":2,"c":3,"d":4}
--XXXsubpartXXX--