Nuxt.js Auth : no data received by API (php)

I'm using NUXT.js, ans the nuxt/auth module.

I can call my API, but i can't get the data:

My nuxt method:

try {
    let response = await this.$auth.loginWith('local', { data: this.login })
    console.log(response)
} catch (err) {
    console.log(err)
}

In the login data, i have password and email.

My nuxt.config.js :

auth: {
    strategies: {
      local: {
        endpoints: {
          login: {
            url: API_URL_LOGIN,
            method: 'post'
          },
          logout: {
            url: API_URL_LOGOUT,
            method: 'post'
          },
          user: {
            url: API_URL_USER,
            method: 'post'
          }
        }
      }
    },
  },

In my PHP API, I'm trying to collect Email and Password data, but... I have NOTHING in $_POST (or $_GET)

<?php
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Headers: Content-Type, X-Requested-With, Authorization');
header('Access-Control-Allow-Methods: POST, GET, OPTIONS, DELETE, PUT');
header('Content-Type: application/json;charset=utf-8');

$return['post'] = $_POST;
$return['get'] = $_GET;

echo json_encode($return);
?>

And so, with my console.log(response), i have :

Config:
  baseURL: "http://localhost:3000/"
  data: "{"username":"vincent.blondaux@gmail.com","password":"admin"}"
  headers: {Accept: "application/json, text/plain, */*", Content-Type: "application/json;charset=utf-8"}
  method: "post"
  url: "...url.../login.php"
  ...
data:
  get: []
  post: []

Any ideas? Thanks a lot! Vincent