Add document generation & e-signing to your app.

// C#
var http = new HttpClient { BaseAddress = new(baseUrl) };
var token = await http.PostAndReadAsync(
  $"/api/Account/Login?username={u}&password={p}");
http.DefaultRequestHeaders.Authorization = new("Bearer", token);

var docId = await http.PostAsJsonAsync(
  "/api/Document/GenerateDocumentFromJson" +
  "?templateId=42&outputType=Pdf", entries)
  .Result.Content.ReadFromJsonAsync<int>();

var pdf = await http.GetByteArrayAsync(
  $"/api/Document/DownloadDocument?id={docId}&jwtToken={token}");
await File.WriteAllBytesAsync("invoice.pdf", pdf);

// JavaScript / Node
const token = await (await fetch(
  `${base}/api/Account/Login?username=${u}&password=${p}`,
  { method: "POST" })).text();

const docId = await (await fetch(
  `${base}/api/Document/GenerateDocumentFromJson` +
  `?templateId=42&outputType=Pdf`,
  { method: "POST",
    headers: { Authorization: `Bearer ${token}`,
               "Content-Type": "application/json" },
    body: JSON.stringify(entries) })).json();

const pdf = await fetch(`${base}/api/Document/` +
  `DownloadDocument?id=${docId}&jwtToken=${token}`);

# Python
import requests
base = "https://docs.acme.com"

token = requests.post(f"{base}/api/Account/Login",
    params={"username": u, "password": p}).text

doc_id = requests.post(
    f"{base}/api/Document/GenerateDocumentFromJson",
    params={"templateId": 42, "outputType": "Pdf"},
    headers={"Authorization": f"Bearer {token}"},
    json=entries).json()

pdf = requests.get(f"{base}/api/Document/DownloadDocument",
    params={"id": doc_id, "jwtToken": token}).content
open("invoice.pdf", "wb").write(pdf)