Simple but struggling to convert POST request from using URL params to request body

Question

I was making a POST request in the following manner, using URL params (which worked):

var PAYLOAD = `
  <myxmlcontent>
    <attribute name="id">1</attribute>
    <attribute name="FullName">Joe Bloggs</attribute>
  </myxmlcontent>
`

var URL = 'http://www.somewhere.com/integration?apiKey=company&apiToken=123&payload=' + PAYLOAD;

client.request({
  url: URL,
  type: 'POST',
  contentType: 'application/xml'
}).then(
  function(data) {
    console.log(data);
  }
);

But I wish to put the payload data into the request body.

Is this the correct way to do it? I am not sure, but my attempt has proved unsuccessful so far:

var PAYLOAD = `
  <myxmlcontent>
    <attribute name="id">1</attribute>
    <attribute name="FullName">Joe Bloggs</attribute>
  </myxmlcontent>
`

client.request({
  url: 'http://www.somewhere.com/integration',
  type: 'POST',
  contentType: 'application/xml',
  headers: {
    apiKey: 'company',
    apiToken: '123'
  },
  dataType: 'xml',
  data: 'data=' + JSON.stringify(PAYLOAD)
}).then(
  function(data) {
    console.log(data);
  }
);

I am currently building a client-side Zendesk app.

Answer 1

SOLVED. This is what I had to do (thank you):

var PAYLOAD = `
  <myxmlcontent>
    <attribute name="id">1</attribute>
    <attribute name="FullName">Joe Bloggs</attribute>
  </myxmlcontent>
`

var URL = 'http://www.somewhere.com/integration';

client.request({
  url: URL,
  type: 'POST',
  contentType: 'application/x-www-form-urlencoded',
  dataType: 'xml',
  data: {
    apiKey: 'company',
    apiToken: '123',
    payload: PAYLOAD
  }
}).then(
  function(data) {
    console.log(data);
  }
);

Helpful article: How are parameters sent in an HTTP POST request?