MinIO ships identity_openid disabled by default. Every MINIO_IDENTITY_OPENID_*
value was already correct, but without MINIO_IDENTITY_OPENID_ENABLE=on the
whole block is inert: the console answered /api/v1/login with
{"loginStrategy":"form"} and never rendered an SSO button.
Also drop MINIO_IDENTITY_OPENID_CLAIM_PREFIX, which was declared with an empty
value. An empty prefix makes the claim resolver prepend nothing and then look
for a nested property that cannot exist, so omitting the key is correct.
ArgoCD owns this Tenant with selfHeal, so the change has to land in git to
survive; a direct kubectl apply was reverted within seconds.