java.lang.AssertionError: 1 expectation failed. Expected status code <200> but was <500> - in restassured -Post endpoint test

I am new to RestAssured, trying to create a test for POST endpoint but it returns 500 when i am executing it. Not sure what the problem is.
Below mentioned is the code:

import static io.restassured.RestAssured.*;
import java.util.HashMap;

import org.json.simple.JSONObject;
import org.testng.annotations.BeforeClass;
import org.testng.annotations.Test;
import io.restassured.RestAssured;
import io.restassured.http.ContentType;


public class Test01_CreateBooking {
	@Test
	public void CreateBooking() {
		JSONObject request = new JSONObject();
	
	request.put("firstname", "Tom");
	request.put("lastname", "Payconiq");
	request.put("totalprice", "677");
	request.put("depositpaid", "true");
	request.put("bookingdates.checkin", "2023-06-06");
	request.put("bookingdates.checkout", "2023-07-07");
	request.put("additionalneeds", "Breakfast");
		
	System.out.println(request.toJSONString());
	 //baseURI = "https://restful-booker.herokuapp.com/booking";
	
	given().
		header("Content-Type", "application/json").
		contentType(ContentType.JSON).
		accept(ContentType.JSON).
		body(request.toJSONString()).
	when().
		post("https://restful-booker.herokuapp.com/booking").
	then().
		statusCode(200)
		.log().all();
	}
	
}

I am expecting a 200 and the record should be created but it retuns 500.Can someone please help.

Its because the json body you are sending is invalid , you are expecting json simple

bookingdates.checkin

to convert to below nested key which won't work, it will treat it as a key only

 "bookingdates": {
            "checkin": ""
        }

What you are sending is this

{
	"firstname": "Tom",
	"additionalneeds": "Breakfast",
	"bookingdates.checkin": "2023-06-06",
	"bookingdates.checkout": "2023-07-07",
	"totalprice": "677",
	"depositpaid": "true",
	"lastname": "Payconiq"
}

and correct way is this

{
	"firstname": "Tom",
	"additionalneeds": "Breakfast",
	"bookingdates": {
		"checkin": "2023-06-06",
		"checkout": "2023-07-07"
	},
	"totalprice": "677",
	"depositpaid": "true",
	"lastname": "Payconiq"
}

You need to created a bookingdates object and then add more keys under it to get proper structure of json

use below code , should work fine

import static io.restassured.RestAssured.given;

import io.restassured.http.ContentType;
import org.json.simple.JSONObject;
import org.junit.Test;

public class Test01_CreateBooking {

	@Test
	public void CreateBooking() {
		JSONObject request = new JSONObject();

		request.put("firstname", "Tom");
		request.put("lastname", "Payconiq");
		request.put("totalprice", "677");
		request.put("depositpaid", "true");
		JSONObject bookingDates = new JSONObject();
		bookingDates.put("checkin", "2023-06-03");
		bookingDates.put("checkout", "2023-07-05");
		request.put("bookingdates", bookingDates);
		request.put("additionalneeds", "Breakfast");

		System.out.println(request.toJSONString());
		//baseURI = "https://restful-booker.herokuapp.com/booking";

		given().contentType(ContentType.JSON) .body(request.toJSONString()).when()
			.post("https://restful-booker.herokuapp.com/booking").then().statusCode(200).log()
			.all();
	}
}