Hi, I have this auth.ts file to handle signin for my app:

import NextAuth from 'next-auth';
import CredentialsProvider from "next-auth/providers/credentials"

export const {
    handlers: { GET, POST },
    auth,
    signIn,
    signOut,
} = NextAuth({
    providers: [
        CredentialsProvider({
            name: 'Credentials',
            credentials: {
                // ...
            },
            async authorize(credentials, req) {
                const res = await fetch("my_api_url", {
                    method: 'POST',
                    body: JSON.stringify({ ... }),
                    headers: { "Content-Type": "application/json" }
                })
                const user = await res.json()

                console.log(res.ok);

                if (res.ok && user) {
                    console.log("we're returning the user object:");
                    console.log(user);
                    return user
                }
                console.log("we're returning null:");
                return null
            }
        })
    ]
})

This connects to an api I have that handles the authentication. This works and on my app at /api/auth/signin I have a form to log in. And the console.log() messages in the cmd do indeed show that the authentication is successful:

true // -> from console.log(res.ok)

we're returning the user object:

{ // -> from console.log(user)
  token: 'theJWTtoken'
}

However, when I am then redirected, and I try to get the session data, I get an empty user object:

{ user: {}, expires: '2024-04-05T17:17:57.992Z' }

Here is how i try to get the session data:

import { auth, signIn, signOut } from '@/auth';

type Props = {}

const Header = async (props: Props) => {
    const session = await auth();
    console.log(session);

    return (
            // ...
    );
};

export default Header;

Any Idea why the session's user object becomes empty, even though I return it?