…-with-trailing-slash

Automatic merge from submit-queue

oidc authentication plugin: don't trim issuer URLs with trailing slashes

The issuer URL passed to the plugin must identically match the issuer
URL returned by OpenID Connect discovery. However, the plugin currently
trims all trailing slashes from issuer URLs, causing a mismatch. Since
the go-oidc client already handles this case correctly, don't trim the
path.

Closes #29749

cc @hanikesn @kubernetes/sig-auth

…r-dont-trim-issuer

Automatic merge from submit-queue

oidc auth provider: don't trim issuer URL

This mirrors a similar side fix for the API server authenticator.
Don't trim the issuer URL provided by the user since OpenID Connect
mandates that this URL exactly matches the URL returned by the
issuer during discovery.

This change only impacts clients attempting to connect to providers that
are non-spec compliant.

No test updates since this is already tested by the go-oidc client
package.

See: https://openid.net/specs/openid-connect-discovery-1_0.html#ProviderConfigurationValidation

Server side fix kubernetes#29860
Updates kubernetes#29749

cc @kubernetes/sig-auth @hanikesn