How to add custom fields in google contacts API V3 with json - google-apps-script

Question

API Request
POST https://www.google.com/m8/feeds/contacts/default/full?alt=json
Body
{
"entry": {
"gd$name": {
"gd$fullName": {
"$t": "Rohit Roy"
},
"gd$givenName": {
"$t": "Rohit"
},
"gd$familyName": {
"$t": "Roy"
}
},
"gd$email": [
{
"address": "royrohit1234#exampledomain.com",
"primary": "true",
"rel": "http://schemas.google.com/g/2005#home"
}
],
"gd$phoneNumber": {
"$t": "[phone]",
"primary": "true",
"rel": "http://schemas.google.com/g/2005#home"
},
"gd$organization": {
"gd$orgName": {
"$t": "XYZ Pvt. ltd."
}
}
}
}
This code is working properly i want to add custom fields to google contacts.
For that i tried convert below XML into JSON.
<gContact:userDefinedField key="chess" value="likes playing black"/>
Like This
"gContact$userDefinedField":{
"key":"food",
"value":"Chinese"
}
But this code is not working with above code so i need help to add custom field with my working code above.

Answer 1

Fortunately i got solution of custom fields, birthday and all other google contact fields with JSON API.
Google Contact API Docs updated and mentioned about Peoples API which is replacement of old google contact API.
So now i am using Peoples API instead of Contacts API V3 which already deprecated.
Click This Link For Peoples API Create Contact API Docs
HTTP Request
POST https://people.googleapis.com/v1/people:createContact
Body
{
"emailAddresses": [
{
"value": "rohitroy#exampledomain.com",
"type": "work"
}
],
"names": [{
"givenName": "John",
"familyName": "Doe"
}],
"birthdays": [
{
"date": {
"year": 1996,
"month": 5,
"day": 2
}
}
],
"userDefined": [
{
"key": "customfield",
"value": "anyvalue-123456"
}
]
}
In the Body userDefined is for custom fields.