I have what seems to be a conceptual doubt about where and how to implement user role logic in a next-auth app and which approach is the most conventional.

Namely when using something like this

providers: [
    Auth0Provider({
        clientId: env.AUTH0_CLIENT_ID,
        clientSecret: env.AUTH0_CLIENT_SECRET,
        issuer: env.AUTH0_ISSUER,
        profile(profile) {
            return {
                id: profile.sub,
                name: profile.name,
                email: profile.email,
                image: profile.picture,
                role: //HERE I CAN SET 
            } as User;
        },
    }),
],

This correctly sets up the role when hardcoded, the Prisma adapter is working too and I can get it all the way to the frontend with the session callback

callbacks: {
    session: ({ session, user }) => ({
        ...session,
        user: {
            ...session.user,
            id: user.id,
            role: user.role,
        },
    }),
},

What I don’t understand is where to get this logic from, how can I send it to next-auth.

The only thing I can come up with is something like setting a cookie with the role, let’s say I have two buttons one for customer signup and another for partner signup, before redirecting to /api/auth/signin I could set a cookie, but this is kind of ugly to do it next-js app router from the client side, and I seem to be missing something obvious here.