API:

import connectDB from "@/lib/monogdb";
import User from "@/models/User";
import { NextResponse } from "next/server";
import bcrypt from "bcryptjs";

connectDB();

export async function POST(request) {
  try {
    // Access Req Body
    const reqBody = await request.json();
    const { name, rno, username, password, role, image } = reqBody;
    console.log(reqBody);

    // Check if user already exists
    const user = await User.findOne({ username });
    if (user) {
      return NextResponse.json(
        { message: "User already exists" },
        { status: 400 }
      );
    }

    // // Check if rno already exists
    const r_no = await User.findOne({ rno });
    if (r_no) {
      return NextResponse.json(
        { message: "Roll Number already exists" },
        { status: 400 }
      );
    }

    // // Hash password
    const salt = await bcrypt.genSalt(10);
    const hashedPassword = await bcrypt.hash(password,salt);

    // Create new user
    const newUser = new User({
      name,
      rno,
      username,
      password: hashedPassword,
      role,
      image,
    });

    // // Save user to DB
    const savedUser = await newUser.save();
    console.log(savedUser);

    return NextResponse.json({ message: "User created successfully" });
  } catch (error) {
    return NextResponse.json({ error: error.message }, { status: 500 });
  }
}

Model:

import mongoose from "mongoose";

const userSchema = new mongoose.Schema(
  {
    name: {
      type: String,
      required: true,
    },
    rno: {
      type: String,
      required: true,
    },
    username: {
      unique: true,
      type: String,
      required: true,
    },
    password: {
      type: String,
      required: true,
    },
    role: {
      type: String,
      required: true,
    },
    image: {
      type: String,
      required: true,
    },
  },
  { timestamps: true }
);

const User = mongoose.models.User || mongoose.model("User", userSchema);

export default User;

POST /auth/register 400 in 8ms
{
  name: 'JohnKeats',
  rno: 'assd1a',
  username: 'asdd',
  password: 'yopp1234a5a',
  role: 'yop',
  image: 'https://www.gravatar.com/avatar'
}
{
  username: 'asdd',
  role: 'yop',
  password: '$2a$10$6seXetoaXtJot9wfLeCjduqfXOS5xHtMO6QvIuql9oAXj.68bkqPe',
  _id: new ObjectId('66ae7a7f73f135dcfb828156'),
  __v: 0
}
 POST /auth/register 200 in 72ms

I'm expected to add 6 fields in the database, but only user role pass is saving