add change in trigger authentication CRD for hashiCorpVault

[raviand]

What's Changed
Added a new field, tokenSecretRef, to the HashiCorp Vault credentials configuration.

This new field allows users to specify a Kubernetes secret containing the Vault token.

The existing token string field will be used as a fallback if tokenSecretRef is not provided.

Why This Is Important
Previously, the HashiCorp Vault token had to be provided directly as a string in the KEDA configuration. This is not a recommended security practice for production environments, as it can expose sensitive information.

This change introduces a more secure way to manage the token by leveraging Kubernetes secrets. This aligns with best practices for handling credentials within a Kubernetes cluster.

How to Use It
Users can now configure their trigger with either the existing token field or the new tokenSecret field. For example:

apiVersion: keda.sh/v1alpha1
kind: TriggerAuthentication
metadata:
  name: {trigger-authentication-mame}
  namespace: default
spec:
  hashiCorpVault:
    address: {hashicorp-vault-address}
    authentication: token
    credential:
      tokenSecretRef: 
        name: {secret-name}
        key: {secret-key}
        parameter: "key"

In the example above, secret-name and secret-key point to the secret containing the token.

KEDA core PR change: kedacore/keda#6996

Checklist

• I have verified that my change is according to the deprecations & breaking changes policy
• Commits are signed with Developer Certificate of Origin (DCO - learn more)
• README is updated with new configuration values (if applicable) learn more
• A PR is opened to update KEDA core (repo) (if applicable, ie. when deployment manifests are modified)

Fixes #