Platform engineering is the discipline of designing and building toolchains and workflows that enable self-service capabilities for software engineering organizations in the cloud-native era.

Platform Engineering

<https://www.conftest.dev/|https://www.conftest.dev/>

+1 for OPA, if by "validation" you mean some sort of policy control around what those manifests contain. Conftest is a nice wrapper around OPA that makes it easier to write tests and run them in an automated way.

<https://kyverno.io/> might be also a nice alternative