How do I store a Firestore document reference as a field from nextjs?

Im creating simple blog posts and trying to connect the post to the logged in user.
When i create a document reference to be stored as a field with reference type, I get a map as shown below:

Here is what I tried

The logged in user is stored in context and the data is sent to an api route along with user as a reference that already exists in the database:

import {useAuth} from '../../context/AuthContext';

page function() {
  const {user} = useAuth();
  const onSubmit = async () => {
    const { title, body } = content;
    await axios.post('/api/post', {title, slug: dashify(title), body, author: doc(db, 'users/' + user.uid)
    setContent({title: '', content: ''}) 
  }
}

the api code is as follows

const handler = async (req, res) => {
    try {
        const posts = await getDocs(postsRef);
        const postsData = posts.docs.map((post) => post.data());
        if (postsData.some((post) => post.slug == "slug")) res.status(406).end();
        else {
            const newPost = await addDoc(collection(db, 'posts'), {
                ...req.body,
                createdAt: serverTimestamp(),
            });
            log(newPost, "post details");
            res.status(200).json({ newPost });
        }
        // res.status(201).json({ author });
    } catch (e) {
        log(e, "error occured post");
        res.status(400).end();
    }
};

export default handler;

>Solution :

Instead of passing a DocumentReference directly from frontend, try passing the document path and then create a DocumentReference object on server side as shown below:

// API request
await axios.post('/api/post', {
  title,
  slug: dashify(title),
  body,
  author: `users/${user.uid}`
})

// Handler
const newPost = await addDoc(collection(db, 'posts'), {
  ...req.body,
  author: doc(db, req.body.author)
  createdAt: serverTimestamp(),
});