add client authentication configuration

Created by: wansir

Signed-off-by: hongming hongming@kubesphere.io

ks-console use Resource Owner Password Credentials Grant Flow issuing access_token. For security reasons, client authentication for confidential clients is required when posting an access token request. client_secret and client_id are configurable.

Related to: https://github.com/kubesphere/kubesphere/pull/3525