Next.js secure authenticaton - next.js

Question

I am trying to make a secure authentication with next.js
I've followed this article because it shows how do to it with api route and proxy server, but I do not understand why he uses this http-proxy module
I did the same thing without it and it seems to work perfectly fine.
Here is my pages/login.js file
import { Button } from '#mui/material'
import { useState } from 'react'
export default function loginPage() {
const [message, setMessage] = useState();
const handleSubmit = async (event) => {
event.preventDefault();
const data = {
username: event.target.username.value,
password: event.target.password.value
};
const response = await fetch('/api/login', {
headers: {
'Content-Type': 'application/json'
},
method: 'POST',
body: JSON.stringify(data),
});
setMessage(response.message);
}
return (
<div className="block">
<form onSubmit={handleSubmit}>
{message ? <p className="message">{message}</p> : ""}
<label htmlFor="first">Username</label>
<input type="text" id="username" name="username" variant="outlined" required />
<label htmlFor="last">Password</label>
<input type="text" id="password" name="password" variant="outlined" required />
<div>
<Button className="btn" type="submit" variant="outlined">Submit</Button>
</div>
</form>
</div>
)
}
Here is my pages/api/[...catchAll].js
import Cookies from "cookies"
export default async function handler(req, res) {
console.log("HERE");
const response = await fetch("http://localhost:7000/register", {
method: "POST",
headers: {
"Content-Type": "application/json"
},
body: JSON.stringify(req.body)
}).then((res) => res.json());
const cookies = new Cookies(req, res);
cookies.set("authorization", response.token, {
httpOnly: true,
sameSite: "lax",
maxAge: 100000
});
res.status(200).json(response)
}
My front-end pages/login.js sends a request to pages/api[...catchAll].js and then a request to my back-end is being made. My back-end returns
{
message: "success",
token: crypto.randomBytes(48).toString('hex')
}
and then pages/api/[...catchAll].js sets my cookies. Why in the article the person uses the httpProxy module ? Is it more secure ? Why ?
I've seen this technique in a lot of places because of secure measurements, but I do not understand why they use this proxy server.
Could someone please explain ?