Upload a document

curl --request POST \
  --url https://api.example.com/v2/documents \
  --header 'Content-Type: multipart/form-data' \
  --form file='@example-file' \
  --form 'name=<string>' \
  --form 'purpose=<string>' \
  --form 'type=<string>' \
  --form 'customerId=<string>'

{
  "id": "<string>"
}