Unity HTTP/1.1 400 Bad Request while fetching data from Mongo Atlas

Question

I'm trying to fetch a collection with Mongo Atlas Data API. In API logs, Status seems as "OK" but i'm getting "Bad Request" error in Unity editor. Am I missing something? Thanks for helps.

using UnityEngine;
using UnityEngine.Networking;
using System.Collections;
using System;
using System.Text;

public class Queries : MonoBehaviour
{
   public static void DumpToConsole(object obj)
{
    var output = JsonUtility.ToJson(obj);
    Debug.Log(output);
}
void OnMouseDown()
{
    StartCoroutine(GetDB());

IEnumerator GetDB() {
WWWForm form = new WWWForm();
form.AddField("dataSource","Cluster0");
form.AddField("database","Herbarium");
form.AddField("collection","Herbs-Specs");
/*byte [] bodyRaw = form.data;
string formInput = Convert.ToBase64String(bodyRaw);*/
UnityWebRequest www = UnityWebRequest.Post("https://data.mongodb-api.com/**********/data/v1/action/find", form);
www.SetRequestHeader("Content-Type", "application/json");
www.SetRequestHeader("Access-Control-Request-Headers", "*");
www.SetRequestHeader("api-key", "***********");
        yield return www.SendWebRequest();

        if (www.result != UnityWebRequest.Result.Success)
        {
            Debug.Log(www.error);
        }
        else
        {
            DumpToConsole(www.downloadHandler.text);
        }
    
    }   
}

}