Next.js app server actions - handling a successful server response

[dopoto]

I'm looking into how to take in use TanStack Form into a Next.js app using server actions:

• https://tanstack.com/form/v1/docs/framework/react/guides/ssr#using-tanstack-form-in-a-nextjs-app-router
• https://github.com/TanStack/form/blob/main/examples/react/next-server-actions/src/app/client-component.tsx
• https://github.com/TanStack/form/blob/main/examples/react/next-server-actions/src/app/action.ts

I might be missing something obvious, but neither the docs or the code examples show how to actually handle the happy path:

• the server action processes the form data and returns a success message:

...
// Your form has successfully validated!
const result = await saveToDb(validatedData)
// how to make this part of the data model being passed between server and client?
return { isSuccess: true}

• the client side code is notified about it and confirms to the user:

// where and how to check this?
if(state.isSuccess === true){
 console.log('Saved')
}

can anybody please point me to some more detailed examples on how to achieve this in a TanStackForm-way?