I want the user who logs in to additionally create a username, in case of not creating it or canceling the transaction the account is not saved in the mongodb database.
I have a problem that does not recognize username in session and in redirect it does not find user.

Here is the code:

import NextAuth from "next-auth";
import { PrismaAdapter } from "@next-auth/prisma-adapter";
import { PrismaClient } from "@prisma/client";
import Google from "next-auth/providers/google";
import GithHub from "next-auth/providers/github";

const prisma = new PrismaClient();

export const { handlers, auth, signIn, signOut } = NextAuth({
adapter: PrismaAdapter(prisma),
providers: [Google, GithHub],
callbacks: {
async signIn({ user, account, profile }) {
const existingUser = await prisma.user.findUnique({
where: { email: user.email as string },
});

if (existingUser && existingUser.username) {
return true;
}

if (!existingUser) {
return true;
}

return false;
},
async session({ session, token, user }) {
session.user.username = user.username;
return session;
},
async redirect({ url, baseUrl }) {
if (!user.username) {
return ${baseUrl}/create-username;
}
return url;
},
},
session: {
strategy: "jwt",
},
});
Errors: Property 'username' does not exist on type 'AdapterUser & User'.
Cannot find name 'user'.

then i show the prisma scheme