Bugfix : Make match.resources.kinds required

[vyankyGH]

Related issue

closes #1734

What type of PR is this

Validate matchResorce kind object in cluster policy.

/kind feature

Proposed Changes

After this PR
IF Someone not added match resource kind policy will not get apply.

Proof Manifests

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata: 
  name: disallow-bind-mounts
spec: 
  validationFailureAction: enforce
  rules: 
  - name: validate-hostPath
    match: 
      resources: 
        kinds: 
    validate: 
      message: "Host path volumes are not allowed"
      pattern: 
        spec: 
          =(volumes): 
          - X(hostPath): "null"

When the above policy will be applied, the following error will be generated:

The ClusterPolicy "disallow-bind-mounts" is invalid: spec.rules.match.resources.kinds: Invalid value: "null": spec.rules.match.resources.kinds

apiVersion : kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: policy-to-monitor-root-user-access
spec:
  validationFailureAction: audit
  rules:
  - name: monitor-annotation-for-root-user-access
    match:
      resources:
        selector:
            matchLabels:
                AllowRootUserAccess: "true"      
    validate:
      message: "Label provisioner.wg.net/cloudprovider is required"
      pattern:
        metadata:
          labels:
            provisioner.wg.net/cloudprovider: "*"

Error from server: error when creating ".\\policy.yaml": admission webhook "validate-policy.kyverno.svc" denied the request: At least one element must be specified in a kind block. The kind attribute is mandatory when working with the resources element

Checklist

• I have read the contributing guidelines.
• I have added tests that prove my fix is effective or that my feature works.
• My PR contains new or altered behavior to Kyverno and
  • [] I have added or changed the documentation myself in an existing PR and the link is:
  Doc: match.resources.kinds mandatory website#143
  • I have raised an issue in kyverno/website to track the doc update and the link is:
  Doc update for match kind is mandatory website#142
  • [] I have read the PR documentation guide and followed the process including adding proof manifests to this PR.

Further Comments