Describe the solution you'd like

There are scenarios where using Hashicorp Vault Kubernetes Auth, one needs to use a JWT with custom audience.
Right now one only can define a JWT through a static secret which could not be used in a GitOps deployment, or through service account name which can't customize JWT

What is the added value?

Enabling TokenRequest API to fetch service account tokens in Hashipotp Vault Kubernetes Auth will increase the scenarios where this secure auth method could be used.

Observations (Constraints, Context, etc):

The TokenRequest API it's being used alredy in Hashicorp Vault JWT/OIDC Auth, see field kubernetesServiceAccountToken.