Hi,

 I wonder if it's possible to just check the SSO state with a confidential client. My use case is the following one:

- I have a website which uses a confidential client to login with Keycloak.

- I want to add autologin to this website.

- So I use the javascript adapter with the following option object for the init method: { onLoad: 'check-sso' }. The javascript adapter is built without the secret key in its constructor (obviously if I put the secret key in there, there's no point to use a confidential client at all).

But Keycloak fails with a "type=CODE_TO_TOKEN_ERROR, error=invalid_client_credentials" error.

So I don't know how feasible or secure is to just check that the Keycloak session inside the cookie of the user's browser is still valid. In my case, the browser doesn't need to get the user info, access token, etc, because what I'll do is redirect the user to the Keycloak login page with the confidential client afterwards is the operation is successful. Since the Keycloak session is valid, Keycloak should redirect back with the authentication code without asking credentials to the user.

Additional note: the CORS header isn't added to 400 responses in Keycloak, so it was a bit confusing looking at the JS console in the browser, because it complained about CORS but it was just Keycloak giving the 400 response without the allow-origin header.