BREAKING CHANGE: Change trivy k8s API

[josedonizetti]

Summary

Specify targets to be scanned by trivy k8s (cluster, all, or resources eg: deployment/lua) .

Before

# Scanning a full cluster (including cluster level resources)

$ trivy k8s --report=summary

# Scanning namespaces

$ trivy k8s --report=summary --namespace=default
$ trivy k8s --report=summary --namespace=kube-system

# Scanning resources

$ trivy k8s pod lua
$ trivy k8s deploy orion
$ trivy k8s statefulset milky

After

# Root command shows help message, like other trivy commands
$ trivy k8s

# Scanning a full cluster (including cluster level resources)

$ trivy k8s --report=summary cluster

# Scanning namespaces

$ trivy k8s --report=summary all # scans the default namespace
$ trivy k8s --report=summary --namespace=kube-system all

# Scanning resources (works in the same way)

$ trivy k8s pod lua
$ trivy k8s deploy orion
$ trivy k8s statefulset milky

Description

To be consistent with other trivy commands, we are changing the trivy k8s API to expect targets, and print a help message on the root command without any target.