curl --request POST \
  --url https://app.sajn.se/api/v1/documents \
  --header 'Content-Type: application/json' \
  --header 'authorization: <authorization>' \
  --data '{
  "name": "<string>",
  "externalId": "<string>",
  "expiresAt": "<any>",
  "type": "SIGNABLE",
  "templateId": "<string>",
  "signers": [],
  "customFields": [
    {
      "customInputId": "<string>",
      "value": "<string>"
    }
  ]
}'

{
  "documentId": "<string>",
  "externalId": "<string>",
  "expiresAt": "<any>",
  "signers": [
    {
      "signerId": "<string>",
      "name": "<string>",
      "email": "jsmith@example.com",
      "token": "<string>",
      "role": "SIGNER",
      "signingOrder": 123,
      "signingUrl": "<string>"
    }
  ]
}