chore(docs): update migrating-to-v5 docs

[halvaradop]

☕️ Reasoning

This pull request updates the documentation in the migrating-to-v5 section by expanding and improving the existing content. A new Route Handlers tab was added to the details section, providing guidance on how to use NextAuth.js v5 with Route Handlers. Additionally, the Client Component section was revised to address multiple issues raised by the community regarding unclear documentation.

The format:write script was also run to ensure consistent formatting across the documentation files.

It’s been a while since my last contribution to the project, so I’m glad to be back and help improve the docs.

Key Changes

• Updated the Client Component section
• Added a new Route Handlers section
• Ran the format:write script

🧢 Checklist

• Documentation
• Tests
• Ready to be merged

🎫 Affected issues

#12767

📌 Resources

• Security guidelines
• Contributing guidelines
• Code of conduct
• Contributing to Open Source

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[vercel]

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[ThangHuuVu]

in Route handler, we can just use the req.auth like the other part of the docs here: https://authjs.dev/reference/nextjs#in-route-handlers
I think we can just link to this page here, HDYT?

[halvaradop]

You're right, however, this method of accessing the session isn't working as expected. It's been reported by users that req.auth often returns null. Because of this, I’ve chosen to access the session directly using the auth() function instead of the wrapper.

Test Case

I created a demo using the Credentials provider. After logging in, I set up an endpoint to access the session via the wrapper. During testing, all values passed through the Credentials provider are authenticated correctly. The session is properly stored, and cookies are created with the authjs prefix.

When accessing the session using the auth() function directly—or via useSession()—everything works as expected. However, accessing the session through request.auth consistently returns null.

Tell me what you think, and I’ll make the necessary changes.

export const GET = auth((request) => {
    const session = request.auth
    if(!session) {
        return NextResponse.json(
            { message: "No session" }, 
            { status: 401 }
        )
    }
    return NextResponse.json({ 
        auth: session, 
        message: "GET /api/session"
    }, { status: 200 }) 
})