fix: default addAcceptedScopesHeader and addAuthorizedScopesHeader to true - #512

Summary

addAcceptedScopesHeader and addAuthorizedScopesHeader are documented as defaulting to true, both on OAuth2Server and on AuthenticateHandler. Only OAuth2Server#authenticate() actually applied that default. AuthenticateHandler itself threw InvalidArgumentError: Missing parameter: addAcceptedScopesHeader whenever scope was set without them.

That breaks OAuth2Server#authorize() for any server configured with a scope option and no custom authenticateHandler. The constructor docs say server options are used as defaults for every method, so scope reaches the default AuthenticateHandler that AuthorizeHandler creates, but the header defaults don't. authorize() then throws synchronously, without even returning a rejected promise:

const server = new OAuth2Server({ model, scope: ['read'] });
await server.authenticate(request, response); // works
server.authorize(request, response);          // throws InvalidArgumentError: Missing parameter: `addAcceptedScopesHeader`

This PR applies the documented default (true when undefined) in the AuthenticateHandler constructor. That one change fixes authorize(), makes direct AuthenticateHandler use match its JSDoc, and keeps explicit false (or other) values as passed. The docs already describe this behaviour, so no doc changes are needed. OAuth2Server#authenticate() keeps its own explicit defaults, which are now redundant but harmless.

Linked issue(s)

None. Found while reviewing other open PRs.

Involved parts of the project

• lib/handlers/authenticate-handler.js: constructor option defaults
• The authorization endpoint (OAuth2Server#authorize() → AuthorizeHandler → default AuthenticateHandler)

Added tests?

Yes. Each of these fails on master with Missing parameter: … and passes here:

• Server integration › authorize() › should set the scopes headers by default if scope is set on the server resolves with the code and sets X-Accepted-OAuth-Scopes / X-OAuth-Scopes.
• AuthenticateHandler integration › constructor() has two tests that each default one option to true while keeping the other's explicit false.

The two tests that asserted the old Missing parameter errors are replaced by those default tests. biome check . is clean and the full mocha suite passes (465).

OAuth2 standard

Not affected. X-Accepted-OAuth-Scopes / X-OAuth-Scopes are informational, non-standard headers.

Reproduction

const OAuth2Server = require('@node-oauth/oauth2-server');
const { Request, Response } = OAuth2Server;

const server = new OAuth2Server({
  scope: ['read'],
  model: {
    getAccessToken: () => ({ user: {}, accessTokenExpiresAt: new Date(Date.now() + 10000), scope: ['read'] }),
    verifyScope: () => true,
    getClient: () => ({ id: 'c', grants: ['authorization_code'], redirectUris: ['http://example.com/cb'] }),
    saveAuthorizationCode: (code) => code,
  },
});
const request = new Request({
  method: 'GET',
  headers: { Authorization: 'Bearer foo' },
  query: { state: 'xyz' },
  body: { client_id: 'c', response_type: 'code' },
});

server.authorize(request, new Response());
// master:  throws InvalidArgumentError: Missing parameter: `addAcceptedScopesHeader`
// this PR: resolves with the authorization code and sets both scopes headers

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