Can't use kubelogin with Gitlab because of the code_verifier parameter

[Place1]

Kubelogin is sending the code_verifier parameter which isn't supported on Gitlab.

Here's an issue on Gitlab's issue tracker: https://gitlab.com/gitlab-org/gitlab/-/issues/213643

Perhaps PKCE should not be used if the OIDC provider doesn't support it? I believe this can be determined at runtime via the discovery endpoint.

[int128]

It may possible to determine the provider supports PKCE by code_challenge_methods_supported of the discovery document as RFC8414.

For example, Google returns the following discovery document:

 "code_challenge_methods_supported": [
  "plain",
  "S256"
 ],

GitLab's discovery document does not contain code_challenge_methods_supported.

[int128]

Would you check the new release v1.19.1? Thank you for your contribution.