docs: Fix safeGetSession Type Definition and Missing Import in SvelteKit Guide (#26280)

[Surjeet9700]

The type definition for the safeGetSession function in app.d.ts has been updated to include an optional user property in the returned Promise. This change ensures compatibility with the latest version of @supabase/supabase-js.

I have read the CONTRIBUTING.md file.

YES

What kind of change does this PR introduce?

docs update

What is the current behavior?

The provided type definition for safeGetSession in app.d.ts causes a TypeScript error in files like +layout.ts because it expects a user property that doesn't always exist in the return value.
The app.d.ts file is missing an import for the User type, causing another TypeScript error.

What is the new behavior?

The user property in the safeGetSession return type is marked as optional (user?: User | null) to accommodate cases where it might not be present.
The missing User type import is added to app.d.ts.
This resolves the TypeScript errors and ensures the code compiles correctly without unexpected type mismatches.

Feel free to include screenshots if it includes visual changes.

Additional context

This PR addresses issue #26280 The changes are minimal but important for ensuring the accuracy and usability of the documentation and type definitions.

Add any other context or screenshots.

`// src/app.d.ts
import type { SupabaseClient, Session, User } from '@supabase/supabase-js'; // Added User import

declare global {
namespace App {
interface Locals {
supabase: SupabaseClient;
safeGetSession(): Promise<{ session: Session | null; user?: User | null }>; // user is now optional
}
interface PageData {
session: Session | null;
user?: User | null; // user is now optional
}
// interface Error {}
// interface Platform {}
}
}
`

[vercel]

@Surjeet9700 is attempting to deploy a commit to the Supabase Team on Vercel.

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[charislam]

Thanks @Surjeet9700!

Definitely the type needs to be added, but the return type for safeGetSession I'm a bit confused by. I'm looking at the function definition and not seeing a case where user would be missing, mind pointing me to the location?

[Surjeet9700]

You're absolutely right, I apologize for the confusion. I was working under the assumption that the safeGetSession function might not always return a user object.

However, after re-examining the implementation within the context of this project, I can confirm that the function indeed consistently returns a user object along with the session. Therefore, the optional user property might not be necessary.

I'll update the pull request to remove the optional nature of the user property in the safeGetSession return type. Thank you for bringing this to my attention!