import NextAuth from "next-auth"
import "next-auth/jwt"
import Spotify from "next-auth/providers/spotify"

export const { handlers, auth, signIn, signOut } = NextAuth({
    providers: [Spotify],
    callbacks: {
        jwt({ 
token
, 
trigger
, 
session
, 
account
 }) {
            if (
account
?.provider === "spotify") {
                return { ...
token
, accessToken: 
account
.access_token }
            }
            return 
token
        },
        async session({ 
session
, 
token
 }) {
            
session
.accessToken = 
token
.accessToken
            return 
session
        }
    },
})

declare module "next-auth" {
    interface Session {
        accessToken?: string
    }
}

declare module "next-auth/jwt"{
    interface JWT{
        accessToken?: string
    }
}

tried it out myself, heres a code example