When content is decoded from an `eyaml` backend, hiera should automatically mark it as a Sensitive data type. Currently it is just converted to the backing data type.
This can lead to unintended disclosure of the encrypted values within modules.
This would need to be done in the eyaml module since it can read plain yaml as well as the specially encoded eyaml content. Many users rely on eyaml backend to also read plain text so cannot be done in hiera as it would not know if the source was encoded or not.