Session user id does not get added to session

import { PrismaAdapter } from '@auth/prisma-adapter';
import { type DefaultSession, type NextAuthOptions, getServerSession } from 'next-auth';
import type { Adapter } from 'next-auth/adapters';
import DiscordProvider from 'next-auth/providers/discord';

import { env } from 'env';
import { db } from 'server/db';

/**
 * Module augmentation for `next-auth` types. Allows us to add custom properties to the `session`
 * object and keep type safety.
 *
 * @see https://next-auth.js.org/getting-started/typescript#module-augmentation
 */
declare module 'next-auth' {
    interface Session extends DefaultSession {
        user: {
            id: string;
            // ...other properties
            // role: UserRole;
        } & DefaultSession['user'];
    }

    // interface User {
    //   // ...other properties
    //   // role: UserRole;
    // }
}

/**
 * Options for NextAuth.js used to configure adapters, providers, callbacks, etc.
 *
 * @see https://next-auth.js.org/configuration/options
 */
export const authOptions: NextAuthOptions = {
    session: {
        strategy: 'jwt',
    },
    callbacks: {
        session: ({ session, token }) => ({
            ...session,
            user: {
                ...session.user,
                id: token.sub,
            },
        }),
    },
    adapter: PrismaAdapter(db) as Adapter,
    providers: [
        DiscordProvider({
            clientId: env.DISCORD_CLIENT_ID,
            clientSecret: env.DISCORD_CLIENT_SECRET,
        }),
    ],
    pages: {
        signIn: '/auth/login',
    },
};

/**
 * Wrapper for `getServerSession` so that you don't need to import the `authOptions` in every file.
 *
 * @see https://next-auth.js.org/configuration/nextjs
 */
export const getServerAuthSession = () => getServerSession(authOptions);