* Users may have external CA setups that pre-configure certificates.
* The CaClient can use JWT token for the initial setup, then switch to mTLS certificates.

Note that `OUTPUT_CERTS` can be used to refresh certificates using previously provisioned certificates, by configuring
the ca client to use certificates written to the same directory we have configured them to be written to.

## Authentication

  //
  //   1. Old signer that is unaware of the field (such as the in-tree
  //      implementations prior to v1.22)
  //   2. Signer whose configured maximum is shorter than the requested duration
  //   3. Signer whose configured minimum is longer than the requested duration
  //
  // The minimum valid value for expirationSeconds is 600, i.e. 10 minutes.
  //
  // +optional

and a different team may maintain the control plane components (which are highly security sensitive).

The install is organized in 'environments' - each environment consists of a set of components
in different namespaces that are configured to work together. Regardless of 'environment',
workloads can talk with each other and obey the Istio configuration resources, but each environment
can use different Istio versions and different configuration defaults.

# Port and basic host configuration

In order to configure the Service object, the install/upgrade needs to provide a list of all ports.
In the past, this was done when installing/upgrading full istio, and involved some duplication - ports configured
both in upgrade, Gateway and VirtualService.

### Examples

#### Configuring mesh configuration settings

Any [Mesh Config](https://istio.io/latest/docs/reference/config/istio.mesh.v1alpha1/) options can be configured like below:

```yaml
meshConfig:
  accessLogFile: /dev/stdout
```

#### Revisions

Control plane revisions allow deploying multiple versions of the control plane in the same cluster.

  // An empty or nil nodeSelector selects all nodes.
  // This field is immutable.
  // +optional
  optional k8s.io.api.core.v1.NodeSelector nodeSelector = 1;

  // perNodeHostBits defines the number of host bits to be configured per node.
  // A subnet mask determines how much of the address is used for network bits
  // and host bits. For example an IPv4 address of 192.168.0.0/24, splits the

## Acceptable Pull Requests

Helm charts `values.yaml` represent a complex user facing API that tends to grow uncontrollably over time
due to design choices in Helm.
The underlying Kubernetes resources we configure have 1000s of fields; given enough users and bespoke use cases,
eventually someone will want to customize every one of those fields.

with the Service and bound to the namespace, it is recommended to:

1. Install the new gateway in a new namespace.
2. Copy any TLS certificate to the new namespace, and configure the domains.
3. Checking the new gateway work - for example by overriding the IP in /etc/hosts
4. Modify the DNS server to add the A record of the new namespace
5. Check traffic