curl --request POST \
  --url https://api.hubapi.com/engagements/v1/engagements \
  --header 'Content-Type: application/json' \
  --data '
{
  "engagement": {
    "active": true,
    "ownerId": 123,
    "timestamp": 123
  },
  "associations": {
    "contactIds": [
      123
    ],
    "companyIds": [
      123
    ],
    "dealIds": [
      123
    ],
    "ownerIds": [
      123
    ],
    "ticketIds": [
      123
    ]
  },
  "attachments": [
    {
      "id": 123
    }
  ],
  "metadata": {}
}
'

import requests

url = "https://api.hubapi.com/engagements/v1/engagements"

payload = {
    "engagement": {
        "active": True,
        "ownerId": 123,
        "timestamp": 123
    },
    "associations": {
        "contactIds": [123],
        "companyIds": [123],
        "dealIds": [123],
        "ownerIds": [123],
        "ticketIds": [123]
    },
    "attachments": [{ "id": 123 }],
    "metadata": {}
}
headers = {"Content-Type": "application/json"}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {'Content-Type': 'application/json'},
  body: JSON.stringify({
    engagement: {active: true, ownerId: 123, timestamp: 123},
    associations: {
      contactIds: [123],
      companyIds: [123],
      dealIds: [123],
      ownerIds: [123],
      ticketIds: [123]
    },
    attachments: [{id: 123}],
    metadata: {}
  })
};

fetch('https://api.hubapi.com/engagements/v1/engagements', 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://api.hubapi.com/engagements/v1/engagements",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'engagement' => [
        'active' => true,
        'ownerId' => 123,
        'timestamp' => 123
    ],
    'associations' => [
        'contactIds' => [
                123
        ],
        'companyIds' => [
                123
        ],
        'dealIds' => [
                123
        ],
        'ownerIds' => [
                123
        ],
        'ticketIds' => [
                123
        ]
    ],
    'attachments' => [
        [
                'id' => 123
        ]
    ],
    'metadata' => [
        
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($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://api.hubapi.com/engagements/v1/engagements"

	payload := strings.NewReader("{\n  \"engagement\": {\n    \"active\": true,\n    \"ownerId\": 123,\n    \"timestamp\": 123\n  },\n  \"associations\": {\n    \"contactIds\": [\n      123\n    ],\n    \"companyIds\": [\n      123\n    ],\n    \"dealIds\": [\n      123\n    ],\n    \"ownerIds\": [\n      123\n    ],\n    \"ticketIds\": [\n      123\n    ]\n  },\n  \"attachments\": [\n    {\n      \"id\": 123\n    }\n  ],\n  \"metadata\": {}\n}")

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

	req.Header.Add("Content-Type", "application/json")

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

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

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://api.hubapi.com/engagements/v1/engagements")
  .header("Content-Type", "application/json")
  .body("{\n  \"engagement\": {\n    \"active\": true,\n    \"ownerId\": 123,\n    \"timestamp\": 123\n  },\n  \"associations\": {\n    \"contactIds\": [\n      123\n    ],\n    \"companyIds\": [\n      123\n    ],\n    \"dealIds\": [\n      123\n    ],\n    \"ownerIds\": [\n      123\n    ],\n    \"ticketIds\": [\n      123\n    ]\n  },\n  \"attachments\": [\n    {\n      \"id\": 123\n    }\n  ],\n  \"metadata\": {}\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.hubapi.com/engagements/v1/engagements")

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

request = Net::HTTP::Post.new(url)
request["Content-Type"] = 'application/json'
request.body = "{\n  \"engagement\": {\n    \"active\": true,\n    \"ownerId\": 123,\n    \"timestamp\": 123\n  },\n  \"associations\": {\n    \"contactIds\": [\n      123\n    ],\n    \"companyIds\": [\n      123\n    ],\n    \"dealIds\": [\n      123\n    ],\n    \"ownerIds\": [\n      123\n    ],\n    \"ticketIds\": [\n      123\n    ]\n  },\n  \"attachments\": [\n    {\n      \"id\": 123\n    }\n  ],\n  \"metadata\": {}\n}"

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

{
  "engagement": {},
  "associations": {},
  "attachments": [
    {}
  ],
  "metadata": {}
}