Calendar API Event Attendees Response Status always changes to "Needs Action" - google-calendar-api

Question

I am doing callout from salesforce to google calendar api to upsert a google event. when i make the request, it always changes the attendee status to "NeedsAction", so when I sent request to google, attendee status was "Accepted" but in response i got "NeedsAction". Why google always changes the attendee response. Please help if anyone knows. Thanks
Request Body :
{
"kind" : "calendar#event",
"summary" : "nice 13 val",
"description" : "this is new",
"location" : "3 value friday",
"start" : {
"dateTime" : "2020-08-13T12:30:00+05:00"
},
"end" : {
"dateTime" : "2020-08-13T13:30:00+05:00"
},
"attendees" : [ {
"email" : "mohit.kumar#test.in",
"organizer" : true,
"responseStatus" : "accepted"
}, {
"email" : "test#gmail.com",
"responseStatus" : "accepted"
} ]
}
Callout :
Http http = new Http();
HttpRequest httpReq = new HttpRequest();
httpReq.setEndpoint('https://www.googleapis.com/calendar/v3/calendars/mohit.kumar#test.in/events/'+objEvent.Google_Event_Id__c);
httpReq.setTimeout(30000);
httpReq.setHeader('Content-Type', 'application/json');
httpReq.setMethod('POST');
httpReq.setHeader('X-HTTP-Method-Override','PATCH');
httpReq.setHeader('Authorization', 'Bearer ' + accessToken);
String reqBody = createEventBody(objEvent, googleSettingInfo);
if (String.isNotBlank(reqBody)) {
httpReq.setBody(reqBody);
}
if (httpReq.getBody() != null && httpReq.getBody() != '') {
HttpResponse httpRes = http.send(httpReq);
System.debug('code: ' + httpRes.getStatusCode());
if (httpRes.getStatusCode() == 200) {
System.debug('response: ' + httpRes);
System.debug('create event response body: ' + httpRes.getBody());
}
}
getting attendees response always as "needs Action" while this should be "accepted" for "test#gmail.com"
{
"created": "2020-08-11T18:51:41.000Z",
"updated": "2020-08-28T06:48:49.972Z",
"summary": "nice 13 val",
"description": "this is new",
"location": "3 value friday",
"creator": {
"email": "mohit.kumar#test.in",
"self": true
},
"organizer": {
"email": "mohit.kumar#test.in",
"self": true
},
"start": {
"dateTime": "2020-08-13T14:00:00+05:30"
},
"end": {
"dateTime": "2020-08-13T15:00:00+05:30"
},
"sequence": 16,
"attendees": [
{
"email": "test#gmail.com",
"responseStatus": "needsAction"
},
{
"email": "mohit.kumar#test.in",
"organizer": true,
"self": true,
"responseStatus": "accepted"
}
],

Answer 1

Proposed modification:
What about modifying the createEventBody function in order to create a simple JSON object that will only contain the attendees information with the updated statuses.
This will leverage correctly the PATCH semantics and helps a lot on improving readability.
I tested it myself and your generated JSON object returns an error on the start property. Removing that will help you solve that error too. Finally I tested that passing the attendees property to the PATCH method will work as intended.
You can try using the "Try this API" functionality before actually update your code.
Reference:
Events patch