create-user.js

const newUser = {
  userName: "[email protected]",
  firstName: "John",
  lastName: "Doe",
  ...
};
  
const request = require('request');
const options = {
  method: 'POST',
  url: 'http://localhost:3000/v1/users',
  headers: {
    'Content-Type': 'application/json'
  },
  body: JSON.stringify(newUser)
};

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