Add Istio Operator install guide (#4790)

* Added operator install guide

Added draft of operator install doc

Added entries to dict and fixed typo

Fixed tip syntax error

Moved install docs to new en folder structure

Toned-down intro, bash command fixes, reordered subsections

* PR review feedback, link from feature status page

* Fixed install verification example

content/en/about/feature-stages/index.md

@@ -91,6 +91,7 @@ The 'Authorization (RBAC)' runtime is considered Beta.  However, its API is stil
 
 | Feature           | Phase
 |-------------------|-------------------
+| [Operator installation](/docs/setup/install/operator/)        | Alpha
 | [Kubernetes: Envoy Installation and Traffic Interception](/docs/setup/)        | Stable
 | [Kubernetes: Istio Control Plane Installation](/docs/setup/) | Stable
 | [Attribute Expression Language](/docs/reference/config/policy-and-telemetry/expression-language/)        | Stable

content/en/boilerplates/experimental-feature-warning.md

@@ -0,0 +1,6 @@
+---
+---
+{{< warning >}}
+The following information describes an experimental feature, which is intended
+for evaluation purposes only.
+{{< /warning >}}

content/en/docs/reference/glossary/operator.md

@@ -0,0 +1,4 @@
+---
+title: Operator
+---
+Operators are a method of packaging, deploying and managing a Kubernetes application. For more information, see [Operator pattern](https://kubernetes.io/docs/concepts/extend-kubernetes/operator/).

content/en/docs/setup/install/operator/index.md

@@ -0,0 +1,116 @@
+---
+title: Operator Install [Experimental]
+description: Install and configure Istio using the Istio Operator.
+weight: 25
+keywords: [operator,kubernetes,helm]
+---
+
+{{< boilerplate experimental-feature-warning >}}
+
+Follow this guide to install and configure an Istio mesh using an alternate
+installation method: the Istio {{<gloss operator>}}Operator{{</gloss>}}
+installation.
+
+The Istio Operator installation is a shorter process with the option of
+installing Istio using a one-line command. It has user input
+validation to help prevent installation errors and customization options to
+override any aspect of the configuration.
+
+It has these additional characteristics:
+
+- Descriptive error messages to spot configuration errors easier.
+
+- Installer capable of waiting for Istio pods and services to be in a
+  ready state.
+
+- Fewer dependencies (doesn’t require Helm).
+
+The Operator install is accessed via [`istioctl`](/docs/reference/commands/istioctl/)
+commands.
+
+## Prerequisites
+
+Before you begin, you must meet these prerequisites:
+
+1. [Download the Istio release](/docs/setup/#downloading-the-release).
+1. Perform any necessary [platform-specific setup](/docs/setup/install/platform/).
+1. Check the [Requirements for Pods and
+   Services](/docs/setup/additional-setup/requirements/).
+
+## Install Istio using the default profile
+
+The simplest option is to install Istio using a one-line command:
+
+{{< text bash >}}
+$ istioctl experimental manifest apply
+{{< /text >}}
+
+This command installs a profile named `default` on the cluster defined by your
+Kubernetes configuration. The `default` profile is smaller and more suitable
+for establishing a production environment, unlike the larger profile named
+`demo` that is meant to evaluate a broad set of Istio features.
+
+You can view the profile named `default` by using this command:
+
+{{< text bash >}}
+$ istioctl experimental profile dump
+{{< /text >}}
+
+## Install a different profile
+
+Other Istio configuration profiles can be installed in a cluster using this command:
+
+{{< text bash >}}
+$ istioctl experimental manifest apply --set profile=default
+{{< /text >}}
+
+In the example above, `default` is one of the profile names from the output of
+the `istioctl profile list` command.
+
+## Display the profiles list
+
+You can display the names of Istio configuration profiles that are
+accessible to `istioctl` by using this command:
+
+{{< text bash >}}
+$ istioctl experimental profile list
+{{< /text >}}
+
+Optionally, you can use the `-s` flag with a install package path to see the
+list of configuration profiles available for other Istio versions:
+
+{{< text bash >}}
+$ istioctl experimental profile list -s installPackagePath=https://github.com/istio/istio/releases/tags/1.3.3
+{{< /text >}}
+
+## Inspect/modify a manifest before installation
+
+You can inspect or modify the manifest before installing Istio using these steps:
+
+1. Generate the manifest using this command:
+
+{{< text bash >}}
+$ istioctl experimental manifest generate > $HOME/generated-manifest.yaml
+{{< /text >}}
+
+1. Inspect or modify the manifest as needed.
+1. Then, apply the manifest using this command:
+
+{{< tip >}}
+This command might show transient errors due to resources not being available in
+the cluster in the correct order.
+{{< /tip >}}
+
+{{< text bash >}}
+$ kubectl apply -f $HOME/generated-manifest.yaml
+{{< /text >}}
+
+## Verify a successful installation
+
+You can check if the Istio installation succeeded using the `verify-install` command.
+This compares the installation on your cluster to a manifest you specify
+and displays the results:
+
+{{< text bash >}}
+$ istioctl verify-install -f $HOME/generated-manifest.yaml
+{{< /text >}}