Is your feature request related to a problem? Please describe.
Is it possible to configure when a renewable secret is renewed? The docs state they are renewed after 2/3 of the lease has elapsed which is what we are seeing but we would like to configure this threshold.

https://developer.hashicorp.com/vault/docs/agent-and-proxy/agent/template#renewable-secrets

Describe the solution you'd like
To be able to configure in vault agent config when to renew renewable secrets similar to lease_renewal_threshold (which I believe is only useful for non renewable secrets).

Additional context
We are in the process of adopting vault-agent-injector and would like to more aggressively renew secrets to give us more headroom to fix any issue in case of an outage with vault. This would give us parity with our existing system and make migration seamless.