curl --request POST \
  --url https://vantage-us.abbyy.com/api/publicapi/v1/transactions/{transactionId}/documents/{documentId}/sourceFiles \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: multipart/form-data' \
  --form 'Model={
  "files": [
    {
      "index": 123,
      "registrationParameters": [
        {
          "key": "<string>",
          "value": "<string>"
        }
      ]
    }
  ]
};type=application/json' \
  --form 'Files=@example-file;type=application/octet-stream'

import requests

url = "https://vantage-us.abbyy.com/api/publicapi/v1/transactions/{transactionId}/documents/{documentId}/sourceFiles"

files = { "Files": ("example-file", open("example-file", "rb"), "application/octet-stream") }
files["Model"] = (None, "{\n  \"files\": [\n    {\n      \"index\": 123,\n      \"registrationParameters\": [\n        {\n          \"key\": \"<string>\",\n          \"value\": \"<string>\"\n        }\n      ]\n    }\n  ]\n}", "application/json")
headers = {"Authorization": "Bearer <token>"}

response = requests.post(url, files=files, headers=headers)

print(response.text)

const form = new FormData();
form.append('Model', '{
  "files": [
    {
      "index": 123,
      "registrationParameters": [
        {
          "key": "<string>",
          "value": "<string>"
        }
      ]
    }
  ]
}');
form.append('Files', '<string>');

const options = {method: 'POST', headers: {Authorization: 'Bearer <token>'}};

options.body = form;

fetch('https://vantage-us.abbyy.com/api/publicapi/v1/transactions/{transactionId}/documents/{documentId}/sourceFiles', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://vantage-us.abbyy.com/api/publicapi/v1/transactions/{transactionId}/documents/{documentId}/sourceFiles",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => "-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"Model\"\r\nContent-Type: application/json\r\n\r\n{\r\n  \"files\": [\r\n    {\r\n      \"index\": 123,\r\n      \"registrationParameters\": [\r\n        {\r\n          \"key\": \"<string>\",\r\n          \"value\": \"<string>\"\r\n        }\r\n      ]\r\n    }\r\n  ]\r\n}\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"Files\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n<string>\r\n-----011000010111000001101001--",
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: multipart/form-data"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://vantage-us.abbyy.com/api/publicapi/v1/transactions/{transactionId}/documents/{documentId}/sourceFiles"

	payload := strings.NewReader("-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"Model\"\r\nContent-Type: application/json\r\n\r\n{\r\n  \"files\": [\r\n    {\r\n      \"index\": 123,\r\n      \"registrationParameters\": [\r\n        {\r\n          \"key\": \"<string>\",\r\n          \"value\": \"<string>\"\r\n        }\r\n      ]\r\n    }\r\n  ]\r\n}\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"Files\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n<string>\r\n-----011000010111000001101001--")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Authorization", "Bearer <token>")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://vantage-us.abbyy.com/api/publicapi/v1/transactions/{transactionId}/documents/{documentId}/sourceFiles")
  .header("Authorization", "Bearer <token>")
  .body("-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"Model\"\r\nContent-Type: application/json\r\n\r\n{\r\n  \"files\": [\r\n    {\r\n      \"index\": 123,\r\n      \"registrationParameters\": [\r\n        {\r\n          \"key\": \"<string>\",\r\n          \"value\": \"<string>\"\r\n        }\r\n      ]\r\n    }\r\n  ]\r\n}\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"Files\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n<string>\r\n-----011000010111000001101001--")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://vantage-us.abbyy.com/api/publicapi/v1/transactions/{transactionId}/documents/{documentId}/sourceFiles")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request.body = "-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"Model\"\r\nContent-Type: application/json\r\n\r\n{\r\n  \"files\": [\r\n    {\r\n      \"index\": 123,\r\n      \"registrationParameters\": [\r\n        {\r\n          \"key\": \"<string>\",\r\n          \"value\": \"<string>\"\r\n        }\r\n      ]\r\n    }\r\n  ]\r\n}\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"Files\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n<string>\r\n-----011000010111000001101001--"

response = http.request(request)
puts response.read_body

{
  "type": "<string>",
  "title": "<string>",
  "status": 123,
  "detail": "<string>",
  "instance": "<string>"
}

{
  "type": "<string>",
  "title": "<string>",
  "status": 123,
  "detail": "<string>",
  "instance": "<string>"
}

{
  "type": "<string>",
  "title": "<string>",
  "status": 123,
  "detail": "<string>",
  "instance": "<string>"
}

{
  "type": "<string>",
  "title": "<string>",
  "status": 123,
  "detail": "<string>",
  "instance": "<string>"
}