Backend not receiving body of the request via AXIOS or Fetch

Question

I’m trying to make a POST request via fetch and via Xios, but something is happening that the request arrives without the body. I used Postman to see if it could be some problem in the backend, however, by Postman the body arrives normal and without problems.

The code of the frontend:

import axios from 'axios';
import { ResultNotification } from '../../core/models/ResultNotification';

class Api {
    private api = axios.create({
        baseURL: 'http://localhost:3300'
    });

    public Post<T>(endpoint: string, body: any): Promise<ResultNotification<T>> {
        let header = new Headers();
        header.append('Content-Type', 'text/plain; application/json');
        header.append('Accept', '*/*');
        return new Promise((resolve, reject) => {
            this.api.post<any, any>(endpoint, body, {
                headers: {
                    'Content-Type': 'text/plain; application/json',
                    'Accept': '*/*',
                }
            })
                // fetch(`http://localhost:3300${endpoint}`, {
                //     method: 'POST',
                //     headers: header,
                //     body: JSON.stringify(body),
                // })
                .then(response => resolve(response.data))
                .catch(err => reject(err));
        });
    }
}

return new Api.Post<User>('/login', { username: "t", password: "t" });

The backend configured to receive the content-type and Accept header:

import { LoginController } from './app/application/controller/LoginController';
import { App, METHOD, HEADER } from 'decorated-router';

@App({
    controllers: [
        LoginController
    ],
    server: {
        port: 3300,
        methods: [METHOD.GET, METHOD.POST],
        headers: [HEADER.ORIGIN, HEADER.XREQUESTEDWITH, HEADER.CONTENTTYPE, HEADER.ACCEPT, HEADER.AUTHORIZATION]
    }
})
class Loader { }

The backend receiving the body:

import { UserDto } from './../../domain/dto/UserDto';
import { Body, Controller, Post } from 'decorated-router';
import { UserService } from './../../domain/service/UserService';

@Controller({
    url: '/login',
    cors: '*',
    auth: null
})
export class LoginController {
    constructor(
        private userService: UserService
    ) { }

    @Post()
    login(@Body() userDto: UserDto) {
        console.log(userDto);
        return this.userService.signIn(userDto);
    }

    @Post('/signup')
    signUp(@Body() userDto: UserDto) {
        return this.userService.signUp(userDto);
    }
}