How do I get the logged-in User ID when creating a post request for that user without using req.params.id? - node.js

Question

Let's say I have an API with a /posts endpoint. Each post in my Mongoose schema has a reference to the user that created it, and each user has an array of references to the posts they created.
When posting as a logged-in user, in order to save that reference I need to send the current logged-in user ID along with the content of the post to the /posts endpoint. I would prefer not to do so through some nested query like /users/:id/posts and then send req.params.id. I would like to post directly to /posts but send the user.id in the request somehow.
User model:
const UserSchema = new Schema({
name: {
type: String,
required: true
},
email: {
type: String,
required: true,
unique: true
},
password: {
type: String,
required: true
},
posts: [{
type: mongoose.Schema.Types.ObjectId,
ref: 'Post'
}]
});
Posts model:
const PostSchema = new Schema({
content: {
type: String,
required: true
},
created: {
type: Date,
default: Date.now
},
user: {
type: mongoose.Schema.Types.ObjectId,
ref: 'User'
}
});
Create new post (need a way to get the user ID since it won't actually be in req.params)
exports.createPost = async function(req, res, next) {
try {
const { content } = req.body; // ideally would get user ID from here
const post = await db.Post.create({
content,
user: req.params.id
});
const postUser = await db.User.findById(req.params.id);
postUser.posts.push(post.id);
await postUser.save();
const newPost = await db.Post.findById(post.id);
const {id, created} = newPost;
return res.status(201).json({
id,
content,
created
})
}
catch(err) {
return next(err);
}
}
I know I'm probably missing something obvious, but I appreciate any suggestions.