UPDATE: TO Admins, can you please close or delete post.

the problem description was wrong. 

my problem is now sorted but it wasn't the one i described below

Hello, 

I working on the app which tries to login to my odoo backend on different hosting.

but when i try to login, I receive error : CORS preflight response did not succeed). Status code: 400.

my request contains following:

  method: "POST",
        headers: {    "Content-Type": "application/json",
    "Accept": "application/json",
    "Access-Control-Allow-Origin": this.#origin },
        data: {
        'jsonrpc':"2.0",
        'params':
         {
            'db': this.#db,
            'login':username,
            'password':password,
        },
        },
        withCredentials: true,
        crossDomain: true,
        baseURL: this.#base_url,
        url: "/web/session/authenticate"

but because of CORS policy, browser sends  another OPTIONS request to server with content-type text/html; charset=utf-8 therefore I receive an error:

/web/session/authenticate: Function declared as capable of handling request of type 'json' but called with a request of type 'http'

anybody know how to overcome this problem?