// renewTime is a time when the current holder of a lease has last
  // updated the lease.
  // +optional
  optional k8s.io.apimachinery.pkg.apis.meta.v1.MicroTime renewTime = 4;

  // leaseTransitions is the number of transitions of a lease between
  // holders.
  // +optional
  optional int32 leaseTransitions = 5;

  // renewTime is a time when the current holder of a lease has last
  // updated the lease.
  // +optional
  optional k8s.io.apimachinery.pkg.apis.meta.v1.MicroTime renewTime = 4;

  // leaseTransitions is the number of transitions of a lease between
  // holders.
  // +optional
  optional int32 leaseTransitions = 5;

  // group=certificates.k8s.io resource=signers resourceName=<the signer name>
  // verb=attest.
  //
  // If signerName is not empty, then the ClusterTrustBundle object must be
  // named with the signer name as a prefix (translating slashes to colons).
  // For example, for the signer name `example.com/foo`, valid
  // ClusterTrustBundle object names include `example.com:foo:abc` and
  // `example.com:foo:v1`.
  //

![CA Flow](docs/ca.svg)

A single SDS request from Envoy goes through a few different layers in istio-agent.

1. First, the request is handled by the SDS server. This is mostly just an intermediate translation layer exposing
   the `SecretManager` to Envoy, without much business logic. For each resource requested by Envoy, the SDS server
   will call `SecretManager.GenerateSecret(resourceName)`