This is a way to expose a OpenVAS / GSAD running in a GKE cluster (Google Kubernetes Engine) to the public internet securely with Google Identity-Aware Proxy in front of it.
This will display the normal GSAD login screen after the Google authentication since the GSAD app code can not handle the Google user identity per default.
With this configuration the default data directory is stored on a persistent disk to make all OpenVAS scan/task/target/etc data persistent.