using RestSharp;


var options = new RestClientOptions("http://localhost:53294/api/v1/List/DocumentTemplate/Items/{documentTemplateId}/Content/{languageCode}");
var client = new RestClient(options);
var request = new RestRequest("");
request.AddHeader("Authorization", "Bearer <token>");
request.AddJsonBody("\"aSDinaTvuI8gbWludGxpZnk=\"", false);
var response = await client.PutAsync(request);

Console.WriteLine("{0}", response.Content);

const options = {
  method: 'PUT',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify('aSDinaTvuI8gbWludGxpZnk=')
};

fetch('http://localhost:53294/api/v1/List/DocumentTemplate/Items/{documentTemplateId}/Content/{languageCode}', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_PORT => "53294",
  CURLOPT_URL => "http://localhost:53294/api/v1/List/DocumentTemplate/Items/{documentTemplateId}/Content/{languageCode}",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "PUT",
  CURLOPT_POSTFIELDS => json_encode('aSDinaTvuI8gbWludGxpZnk='),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: application/json"
  ],
]);

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

curl_close($curl);

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

import requests

url = "http://localhost:53294/api/v1/List/DocumentTemplate/Items/{documentTemplateId}/Content/{languageCode}"

payload = "aSDinaTvuI8gbWludGxpZnk="
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.put(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'PUT',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify('aSDinaTvuI8gbWludGxpZnk=')
};

fetch('http://localhost:53294/api/v1/List/DocumentTemplate/Items/{documentTemplateId}/Content/{languageCode}', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

{
  "Name": "<string>",
  "Description": "<string>",
  "ExternalReference": "<string>",
  "MimeType": "<string>",
  "PluginId": 123
}