How to use @auth/core credentials with .NET webapi JWT bearer authentication

[r1y4h]

I've been trying to figure this out for a couple of weeks now. I am working on a Astro project with React (SSR).
We have an existing .NET WebAPI that uses JWT bearer authentication.

POST /api/authenticate
Body: {
username,
password
}

which returns a JWT token. I understand how to use this JWT token to consume our api's resources.

Astro doesn't have a built in authentication but recommended auth.js in their documentation.
Looking at Auth.js, there's a planned provider for Astro.
But I think it would just be a wrapper to use '@auth/core' just like the other existing providers.
I need our project to move forward while waiting for the official auth.js support for Astro.

I could use '@auth/core' and '@auth/core/providers/credentials' since our authentication is just the basic username and password.

Here's what I don't understand with Auth.js Credentials provider.
When you call POST '/auth/signin', why would it redirect to a login page?
Which I though should call the credentials provider authorize method.

It turns out that /auth/callback is the one that would execute credentials.authorize method.
I learned about this when I check the source code of the unofficial auth.js provider for Astro
https://github.com/nowaythatworked/auth-astro/blob/main/client.ts

So now, in my login form submit, I call the /auth/callback so it executes credentials.authorize.
This works fine until I learned that the authorize method expects a user object in return.

I am not sure if this is the right thing to do this inside my credentials.authorize method?

authorize: async () => {
    //call POST /api/authorize to our .NET webapi.
    // which would return a JWT token

   // call GET /api/user info using the JWT token
   
   // return the user result from GET call.
}

Now my problem is, where should I store the JWT token in Auth.js?
Should I return something like this in my credentials.authorize method?

authorize: async () => {
   // ...
  
   return {
      id: user.id
      token: jwtToken I get from .NET webapi
   }
}

Am I right to choose Auth.JS credentials provider? Or should I choose a different authentication component for my Astor project.
I chose Auth.JS because it doesn't require a database.

I am on the verge of choosing a different React SSR capable framework if I can't make Auth.JS work with Astro.
I really like Astro because it's very easy to use compared to others. I didn't expect to meet a road block with authentication.

I would really appreciate if anyone can give me the right direction.