Send Request with Axios return empty Request in Laravel (API)

When I try to send content of textarea with axios, the request received by Laravel is empty.

axios.defaults.headers.common = {
    'X-Requested-With': 'XMLHttpRequest',
    'X-CSRF-TOKEN' : document.querySelector('meta[name="csrf-token"]').getAttribute('content')
};
async sendMessage(e) {
    if (e.shiftKey === false) {
          this.errors = {};
          e.preventDefault();
          let response = await axios.post('/api/conversations/' + this.$route.params.id, {
               content: this.content,
          });
     }
}

Route::post('/conversations/{user}', 'API\ConversationsController@store')->middleware('can:talkTo,user');

public function store(Request $request, User $user) {
    return ['request' => $request, 'user' => $user];
}

Result in browser :

request: {attributes: {}, request: {}, query: {}, server: {}, files: {}, cookies: {}, headers: {}}
user: {id: 2, name: "JohnDoe1", email: "john1@doe.fr", email_verified_at: null, created_at: null,…}

via Chebli Mohamed