A team must prohibit service-account key creation across a governed resource hierarchy, rather than merely discouraging developers from creating keys. Which approach best fits?

1. Restrict federation using validated token attributes and narrowly scoped IAM bindings.
2. Define and maintain a custom IAM role with the necessary supported permissions.
3. Evaluate the deny policy and its exceptions rather than adding more allow grants.
4. Apply the supported organization-policy restriction on service-account key creation.