Step 1: Create custom domain

curl --location --globoff '{{apiPath}}/environments/{{envID}}/customDomains' \
--header 'Content-Type: application/json' \
--header 'Authorization: Bearer {{accessToken}}' \
--data '{
    "domainName": "custom-domain.example.com",
    "mtlsEnabled": true
}'

var options = new RestClientOptions("{{apiPath}}/environments/{{envID}}/customDomains")
{
  MaxTimeout = -1,
};
var client = new RestClient(options);
var request = new RestRequest("", Method.Post);
request.AddHeader("Content-Type", "application/json");
request.AddHeader("Authorization", "Bearer {{accessToken}}");
var body = @"{" + "\n" +
@"    ""domainName"": ""custom-domain.example.com""," + "\n" +
@"    ""mtlsEnabled"": true" + "\n" +
@"}";
request.AddStringBody(body, DataFormat.Json);
RestResponse response = await client.ExecuteAsync(request);
Console.WriteLine(response.Content);

package main

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

func main() {

  url := "{{apiPath}}/environments/{{envID}}/customDomains"
  method := "POST"

  payload := strings.NewReader(`{
    "domainName": "custom-domain.example.com",
    "mtlsEnabled": true
}`)

  client := &http.Client {
  }
  req, err := http.NewRequest(method, url, payload)

  if err != nil {
    fmt.Println(err)
    return
  }
  req.Header.Add("Content-Type", "application/json")
  req.Header.Add("Authorization", "Bearer {{accessToken}}")

  res, err := client.Do(req)
  if err != nil {
    fmt.Println(err)
    return
  }
  defer res.Body.Close()

  body, err := io.ReadAll(res.Body)
  if err != nil {
    fmt.Println(err)
    return
  }
  fmt.Println(string(body))
}

POST /environments/{{envID}}/customDomains HTTP/1.1
Host: {{apiPath}}
Content-Type: application/json
Authorization: Bearer {{accessToken}}

{
    "domainName": "custom-domain.example.com",
    "mtlsEnabled": true
}

OkHttpClient client = new OkHttpClient().newBuilder()
  .build();
MediaType mediaType = MediaType.parse("application/json");
RequestBody body = RequestBody.create(mediaType, "{\n    \"domainName\": \"custom-domain.example.com\",\n    \"mtlsEnabled\": true\n}");
Request request = new Request.Builder()
  .url("{{apiPath}}/environments/{{envID}}/customDomains")
  .method("POST", body)
  .addHeader("Content-Type", "application/json")
  .addHeader("Authorization", "Bearer {{accessToken}}")
  .build();
Response response = client.newCall(request).execute();

var settings = {
  "url": "{{apiPath}}/environments/{{envID}}/customDomains",
  "method": "POST",
  "timeout": 0,
  "headers": {
    "Content-Type": "application/json",
    "Authorization": "Bearer {{accessToken}}"
  },
  "data": JSON.stringify({
    "domainName": "custom-domain.example.com",
    "mtlsEnabled": true
  }),
};

$.ajax(settings).done(function (response) {
  console.log(response);
});

var request = require('request');
var options = {
  'method': 'POST',
  'url': '{{apiPath}}/environments/{{envID}}/customDomains',
  'headers': {
    'Content-Type': 'application/json',
    'Authorization': 'Bearer {{accessToken}}'
  },
  body: JSON.stringify({
    "domainName": "custom-domain.example.com",
    "mtlsEnabled": true
  })

};
request(options, function (error, response) {
  if (error) throw new Error(error);
  console.log(response.body);
});

import requests
import json

url = "{{apiPath}}/environments/{{envID}}/customDomains"

payload = json.dumps({
  "domainName": "custom-domain.example.com",
  "mtlsEnabled": True
})
headers = {
  'Content-Type': 'application/json',
  'Authorization': 'Bearer {{accessToken}}'
}

response = requests.request("POST", url, headers=headers, data=payload)

print(response.text)

<?php
require_once 'HTTP/Request2.php';
$request = new HTTP_Request2();
$request->setUrl('{{apiPath}}/environments/{{envID}}/customDomains');
$request->setMethod(HTTP_Request2::METHOD_POST);
$request->setConfig(array(
  'follow_redirects' => TRUE
));
$request->setHeader(array(
  'Content-Type' => 'application/json',
  'Authorization' => 'Bearer {{accessToken}}'
));
$request->setBody('{\n    "domainName": "custom-domain.example.com",\n    "mtlsEnabled": true\n}');
try {
  $response = $request->send();
  if ($response->getStatus() == 200) {
    echo $response->getBody();
  }
  else {
    echo 'Unexpected HTTP status: ' . $response->getStatus() . ' ' .
    $response->getReasonPhrase();
  }
}
catch(HTTP_Request2_Exception $e) {
  echo 'Error: ' . $e->getMessage();
}

require "uri"
require "json"
require "net/http"

url = URI("{{apiPath}}/environments/{{envID}}/customDomains")

http = Net::HTTP.new(url.host, url.port);
request = Net::HTTP::Post.new(url)
request["Content-Type"] = "application/json"
request["Authorization"] = "Bearer {{accessToken}}"
request.body = JSON.dump({
  "domainName": "custom-domain.example.com",
  "mtlsEnabled": true
})

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

let parameters = "{\n    \"domainName\": \"custom-domain.example.com\",\n    \"mtlsEnabled\": true\n}"
let postData = parameters.data(using: .utf8)

var request = URLRequest(url: URL(string: "{{apiPath}}/environments/{{envID}}/customDomains")!,timeoutInterval: Double.infinity)
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
request.addValue("Bearer {{accessToken}}", forHTTPHeaderField: "Authorization")

request.httpMethod = "POST"
request.httpBody = postData

let task = URLSession.shared.dataTask(with: request) { data, response, error in
  guard let data = data else {
    print(String(describing: error))
    return
  }
  print(String(data: data, encoding: .utf8)!)
}

task.resume()