Linkedin getToken is broken

[bitliner]

Prerequisites

• [x] I have written a descriptive issue title
• [x] I have searched existing issues to ensure the bug has not already been reported

Fastify version

^5.6.2

Plugin version

^8.1.2

Node.js version

v22.16.0

Operating system

macOS

Operating system version (i.e. 20.04, 11.3, 10)

Sequoia 15.6.1

Description

The code to get the code inside the callback url fails.

I refer to this:

const { token } = await this.linkedinOAuth2.getAccessTokenFromAuthorizationCodeFlow(request);

It throws 400 Bad request

Debugging, the following code:

async getToken(params, httpOptions) {
    const parameters = GrantTypeParams.forGrantType('authorization_code', this.#config.options, params);
    const response = await this.#client.request(this.#config.auth.tokenPath, parameters.toObject(), httpOptions);

    return this.createToken(response);
  }

does not pass all the required parameters.

Indeed, parameters.toObject() is:

{
   code: "..."
grant_type: "authorization_code"
redirect_url:  "http://localhost:3000/login/linkedin/callback"
}

but Linkedin requires also client_id and client_secret as documented here

Link to code that reproduces the bug

https://github.com/bitliner/fastify-oauth-bug

Expected Behavior

The request should not fail with 400